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Date: Fri, 2 Jun 2023 08:22:35 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...el.com>,
Sean Christopherson <seanjc@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Joerg Roedel <jroedel@...e.de>,
Ard Biesheuvel <ardb@...nel.org>
Cc: Andi Kleen <ak@...ux.intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Dario Faggioli <dfaggioli@...e.com>,
Mike Rapoport <rppt@...nel.org>,
David Hildenbrand <david@...hat.com>,
Mel Gorman <mgorman@...hsingularity.net>,
marcelo.cerri@...onical.com, tim.gardner@...onical.com,
khalid.elmously@...onical.com, philip.cox@...onical.com,
aarcange@...hat.com, peterx@...hat.com, x86@...nel.org,
linux-mm@...ck.org, linux-coco@...ts.linux.dev,
linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv13 9/9] x86/tdx: Add unaccepted memory support
On 6/1/23 13:25, Kirill A. Shutemov wrote:
> Hookup TDX-specific code to accept memory.
>
> Accepting the memory is done with ACCEPT_PAGE module call on every page
> in the range. MAP_GPA hypercall is not required as the unaccepted memory
> is considered private already.
>
> Extract the part of tdx_enc_status_changed() that does memory acceptance
> in a new helper. Move the helper tdx-shared.c. It is going to be used by
> both main kernel and decompressor.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
> arch/x86/Kconfig | 2 +
> arch/x86/boot/compressed/Makefile | 2 +-
> arch/x86/boot/compressed/error.c | 19 +++++++
> arch/x86/boot/compressed/error.h | 1 +
> arch/x86/boot/compressed/mem.c | 35 +++++++++++-
> arch/x86/boot/compressed/tdx-shared.c | 2 +
> arch/x86/coco/tdx/Makefile | 2 +-
> arch/x86/coco/tdx/tdx-shared.c | 71 ++++++++++++++++++++++++
> arch/x86/coco/tdx/tdx.c | 70 +----------------------
> arch/x86/include/asm/shared/tdx.h | 2 +
> arch/x86/include/asm/unaccepted_memory.h | 24 ++++++++
> 11 files changed, 160 insertions(+), 70 deletions(-)
> create mode 100644 arch/x86/boot/compressed/tdx-shared.c
> create mode 100644 arch/x86/coco/tdx/tdx-shared.c
> create mode 100644 arch/x86/include/asm/unaccepted_memory.h
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 53bab123a8ee..5c72067c06d4 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -884,9 +884,11 @@ config INTEL_TDX_GUEST
> bool "Intel TDX (Trust Domain Extensions) - Guest Support"
> depends on X86_64 && CPU_SUP_INTEL
> depends on X86_X2APIC
> + depends on EFI_STUB
> select ARCH_HAS_CC_PLATFORM
> select X86_MEM_ENCRYPT
> select X86_MCE
> + select UNACCEPTED_MEMORY
> help
> Support running as a guest under Intel TDX. Without this support,
> the guest kernel can not boot or run under TDX.
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index cc4978123c30..b13a58021086 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -106,7 +106,7 @@ ifdef CONFIG_X86_64
> endif
>
> vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
> -vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o
> +vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o $(obj)/tdx-shared.o
> vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/mem.o
>
> vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
> diff --git a/arch/x86/boot/compressed/error.c b/arch/x86/boot/compressed/error.c
> index c881878e56d3..5313c5cb2b80 100644
> --- a/arch/x86/boot/compressed/error.c
> +++ b/arch/x86/boot/compressed/error.c
> @@ -22,3 +22,22 @@ void error(char *m)
> while (1)
> asm("hlt");
> }
> +
> +/* EFI libstub provides vsnprintf() */
> +#ifdef CONFIG_EFI_STUB
> +void panic(const char *fmt, ...)
> +{
> + static char buf[1024];
> + va_list args;
> + int len;
> +
> + va_start(args, fmt);
> + len = vsnprintf(buf, sizeof(buf), fmt, args);
> + va_end(args);
> +
> + if (len && buf[len - 1] == '\n')
> + buf[len - 1] = '\0';
> +
> + error(buf);
> +}
> +#endif
> diff --git a/arch/x86/boot/compressed/error.h b/arch/x86/boot/compressed/error.h
> index 1de5821184f1..86fe33b93715 100644
> --- a/arch/x86/boot/compressed/error.h
> +++ b/arch/x86/boot/compressed/error.h
> @@ -6,5 +6,6 @@
>
> void warn(char *m);
> void error(char *m) __noreturn;
> +void panic(const char *fmt, ...) __noreturn __cold;
>
> #endif /* BOOT_COMPRESSED_ERROR_H */
> diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
> index 4ecf26576a77..d2b6948a7801 100644
> --- a/arch/x86/boot/compressed/mem.c
> +++ b/arch/x86/boot/compressed/mem.c
> @@ -2,11 +2,44 @@
>
> #include "error.h"
> #include "misc.h"
> +#include "tdx.h"
> +#include <asm/shared/tdx.h>
> +
> +/*
> + * accept_memory() and process_unaccepted_memory() called from EFI stub which
> + * runs before decompresser and its early_tdx_detect().
> + *
> + * Enumerate TDX directly from the early users.
> + */
> +static bool early_is_tdx_guest(void)
> +{
> + static bool once;
> + static bool is_tdx;
> +
> + if (!IS_ENABLED(CONFIG_INTEL_TDX_GUEST))
> + return false;
> +
> + if (!once) {
> + u32 eax, sig[3];
> +
> + cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax,
> + &sig[0], &sig[2], &sig[1]);
> + is_tdx = !memcmp(TDX_IDENT, sig, sizeof(sig));
> + once = true;
> + }
> +
> + return is_tdx;
> +}
>
> void arch_accept_memory(phys_addr_t start, phys_addr_t end)
> {
> /* Platform-specific memory-acceptance call goes here */
> - error("Cannot accept memory");
> + if (early_is_tdx_guest()) {
> + if (tdx_accept_memory(start, end))
> + return;
> + }
> +
> + error("Cannot accept memory: unknown platform\n");
So this is a change in this version. If tdx_accept_memory() fails, you'll
report unknown platform. Wouldn't it be better to have an error message
that indicates a failure in the accept path?
Thanks,
Tom
> }
>
> void init_unaccepted_memory(void)
> diff --git a/arch/x86/boot/compressed/tdx-shared.c b/arch/x86/boot/compressed/tdx-shared.c
> new file mode 100644
> index 000000000000..5ac43762fe13
> --- /dev/null
> +++ b/arch/x86/boot/compressed/tdx-shared.c
> @@ -0,0 +1,2 @@
> +#include "error.h"
> +#include "../../coco/tdx/tdx-shared.c"
> diff --git a/arch/x86/coco/tdx/Makefile b/arch/x86/coco/tdx/Makefile
> index 46c55998557d..2c7dcbf1458b 100644
> --- a/arch/x86/coco/tdx/Makefile
> +++ b/arch/x86/coco/tdx/Makefile
> @@ -1,3 +1,3 @@
> # SPDX-License-Identifier: GPL-2.0
>
> -obj-y += tdx.o tdcall.o
> +obj-y += tdx.o tdx-shared.o tdcall.o
> diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
> new file mode 100644
> index 000000000000..ef20ddc37b58
> --- /dev/null
> +++ b/arch/x86/coco/tdx/tdx-shared.c
> @@ -0,0 +1,71 @@
> +#include <asm/tdx.h>
> +#include <asm/pgtable.h>
> +
> +static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
> + enum pg_level pg_level)
> +{
> + unsigned long accept_size = page_level_size(pg_level);
> + u64 tdcall_rcx;
> + u8 page_size;
> +
> + if (!IS_ALIGNED(start, accept_size))
> + return 0;
> +
> + if (len < accept_size)
> + return 0;
> +
> + /*
> + * Pass the page physical address to the TDX module to accept the
> + * pending, private page.
> + *
> + * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G.
> + */
> + switch (pg_level) {
> + case PG_LEVEL_4K:
> + page_size = 0;
> + break;
> + case PG_LEVEL_2M:
> + page_size = 1;
> + break;
> + case PG_LEVEL_1G:
> + page_size = 2;
> + break;
> + default:
> + return 0;
> + }
> +
> + tdcall_rcx = start | page_size;
> + if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
> + return 0;
> +
> + return accept_size;
> +}
> +
> +bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
> +{
> + /*
> + * For shared->private conversion, accept the page using
> + * TDX_ACCEPT_PAGE TDX module call.
> + */
> + while (start < end) {
> + unsigned long len = end - start;
> + unsigned long accept_size;
> +
> + /*
> + * Try larger accepts first. It gives chance to VMM to keep
> + * 1G/2M Secure EPT entries where possible and speeds up
> + * process by cutting number of hypercalls (if successful).
> + */
> +
> + accept_size = try_accept_one(start, len, PG_LEVEL_1G);
> + if (!accept_size)
> + accept_size = try_accept_one(start, len, PG_LEVEL_2M);
> + if (!accept_size)
> + accept_size = try_accept_one(start, len, PG_LEVEL_4K);
> + if (!accept_size)
> + return false;
> + start += accept_size;
> + }
> +
> + return true;
> +}
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 0d5fe6e24e45..a9c4ba6c5c5d 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -713,46 +713,6 @@ static bool tdx_cache_flush_required(void)
> return true;
> }
>
> -static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
> - enum pg_level pg_level)
> -{
> - unsigned long accept_size = page_level_size(pg_level);
> - u64 tdcall_rcx;
> - u8 page_size;
> -
> - if (!IS_ALIGNED(start, accept_size))
> - return 0;
> -
> - if (len < accept_size)
> - return 0;
> -
> - /*
> - * Pass the page physical address to the TDX module to accept the
> - * pending, private page.
> - *
> - * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G.
> - */
> - switch (pg_level) {
> - case PG_LEVEL_4K:
> - page_size = 0;
> - break;
> - case PG_LEVEL_2M:
> - page_size = 1;
> - break;
> - case PG_LEVEL_1G:
> - page_size = 2;
> - break;
> - default:
> - return 0;
> - }
> -
> - tdcall_rcx = start | page_size;
> - if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
> - return 0;
> -
> - return accept_size;
> -}
> -
> /*
> * Inform the VMM of the guest's intent for this physical page: shared with
> * the VMM or private to the guest. The VMM is expected to change its mapping
> @@ -777,33 +737,9 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
> if (_tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0))
> return false;
>
> - /* private->shared conversion requires only MapGPA call */
> - if (!enc)
> - return true;
> -
> - /*
> - * For shared->private conversion, accept the page using
> - * TDX_ACCEPT_PAGE TDX module call.
> - */
> - while (start < end) {
> - unsigned long len = end - start;
> - unsigned long accept_size;
> -
> - /*
> - * Try larger accepts first. It gives chance to VMM to keep
> - * 1G/2M Secure EPT entries where possible and speeds up
> - * process by cutting number of hypercalls (if successful).
> - */
> -
> - accept_size = try_accept_one(start, len, PG_LEVEL_1G);
> - if (!accept_size)
> - accept_size = try_accept_one(start, len, PG_LEVEL_2M);
> - if (!accept_size)
> - accept_size = try_accept_one(start, len, PG_LEVEL_4K);
> - if (!accept_size)
> - return false;
> - start += accept_size;
> - }
> + /* shared->private conversion requires memory to be accepted before use */
> + if (enc)
> + return tdx_accept_memory(start, end);
>
> return true;
> }
> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index 1ff0ee822961..19228beb4894 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -91,5 +91,7 @@ struct tdx_module_output {
> u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
> struct tdx_module_output *out);
>
> +bool tdx_accept_memory(phys_addr_t start, phys_addr_t end);
> +
> #endif /* !__ASSEMBLY__ */
> #endif /* _ASM_X86_SHARED_TDX_H */
> diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
> new file mode 100644
> index 000000000000..f0ab217b566f
> --- /dev/null
> +++ b/arch/x86/include/asm/unaccepted_memory.h
> @@ -0,0 +1,24 @@
> +#ifndef _ASM_X86_UNACCEPTED_MEMORY_H
> +#define _ASM_X86_UNACCEPTED_MEMORY_H
> +
> +#include <linux/efi.h>
> +#include <asm/tdx.h>
> +
> +static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
> +{
> + /* Platform-specific memory-acceptance call goes here */
> + if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
> + if (tdx_accept_memory(start, end))
> + return;
> + }
> +
> + panic("Cannot accept memory: unknown platform\n");
> +}
> +
> +static inline struct efi_unaccepted_memory *efi_get_unaccepted_table(void)
> +{
> + if (efi.unaccepted == EFI_INVALID_TABLE_ADDR)
> + return NULL;
> + return __va(efi.unaccepted);
> +}
> +#endif
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