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Message-ID: <486fe740-0c2d-9d2b-d490-bdb3215a120c@suse.com>
Date: Thu, 30 Apr 2020 11:49:31 +0200
From: Jürgen Groß <jgross@...e.com>
To: Ashish Kalra <Ashish.Kalra@....com>, pbonzini@...hat.com
Cc: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
joro@...tes.org, bp@...e.de, thomas.lendacky@....com,
x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
srutherford@...gle.com, rientjes@...gle.com,
venu.busireddy@...cle.com, brijesh.singh@....com
Subject: Re: [PATCH v7 11/18] mm: x86: Invoke hypercall when page encryption
status is changed
On 30.04.20 10:45, Ashish Kalra wrote:
> From: Brijesh Singh <Brijesh.Singh@....com>
>
> Invoke a hypercall when a memory region is changed from encrypted ->
> decrypted and vice versa. Hypervisor needs to know the page encryption
> status during the guest migration.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: "Radim Krčmář" <rkrcmar@...hat.com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: x86@...nel.org
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Reviewed-by: Venu Busireddy <venu.busireddy@...cle.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
> arch/x86/include/asm/paravirt.h | 10 +++++
> arch/x86/include/asm/paravirt_types.h | 2 +
> arch/x86/kernel/paravirt.c | 1 +
> arch/x86/mm/mem_encrypt.c | 58 ++++++++++++++++++++++++++-
> arch/x86/mm/pat/set_memory.c | 7 ++++
> 5 files changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index 694d8daf4983..8127b9c141bf 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -78,6 +78,12 @@ static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
> PVOP_VCALL1(mmu.exit_mmap, mm);
> }
>
> +static inline void page_encryption_changed(unsigned long vaddr, int npages,
> + bool enc)
> +{
> + PVOP_VCALL3(mmu.page_encryption_changed, vaddr, npages, enc);
> +}
> +
> #ifdef CONFIG_PARAVIRT_XXL
> static inline void load_sp0(unsigned long sp0)
> {
> @@ -946,6 +952,10 @@ static inline void paravirt_arch_dup_mmap(struct mm_struct *oldmm,
> static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
> {
> }
> +
> +static inline void page_encryption_changed(unsigned long vaddr, int npages, bool enc)
> +{
> +}
> #endif
> #endif /* __ASSEMBLY__ */
> #endif /* _ASM_X86_PARAVIRT_H */
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index 732f62e04ddb..03bfd515c59c 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -215,6 +215,8 @@ struct pv_mmu_ops {
>
> /* Hook for intercepting the destruction of an mm_struct. */
> void (*exit_mmap)(struct mm_struct *mm);
> + void (*page_encryption_changed)(unsigned long vaddr, int npages,
> + bool enc);
>
> #ifdef CONFIG_PARAVIRT_XXL
> struct paravirt_callee_save read_cr2;
> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
> index c131ba4e70ef..840c02b23aeb 100644
> --- a/arch/x86/kernel/paravirt.c
> +++ b/arch/x86/kernel/paravirt.c
> @@ -367,6 +367,7 @@ struct paravirt_patch_template pv_ops = {
> (void (*)(struct mmu_gather *, void *))tlb_remove_page,
>
> .mmu.exit_mmap = paravirt_nop,
> + .mmu.page_encryption_changed = paravirt_nop,
>
> #ifdef CONFIG_PARAVIRT_XXL
> .mmu.read_cr2 = __PV_IS_CALLEE_SAVE(native_read_cr2),
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index f4bd4b431ba1..603f5abf8a78 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -19,6 +19,7 @@
> #include <linux/kernel.h>
> #include <linux/bitops.h>
> #include <linux/dma-mapping.h>
> +#include <linux/kvm_para.h>
>
> #include <asm/tlbflush.h>
> #include <asm/fixmap.h>
> @@ -29,6 +30,7 @@
> #include <asm/processor-flags.h>
> #include <asm/msr.h>
> #include <asm/cmdline.h>
> +#include <asm/kvm_para.h>
>
> #include "mm_internal.h"
>
> @@ -196,6 +198,48 @@ void __init sme_early_init(void)
> swiotlb_force = SWIOTLB_FORCE;
> }
>
> +static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
> + bool enc)
> +{
> + unsigned long sz = npages << PAGE_SHIFT;
> + unsigned long vaddr_end, vaddr_next;
> +
> + vaddr_end = vaddr + sz;
> +
> + for (; vaddr < vaddr_end; vaddr = vaddr_next) {
> + int psize, pmask, level;
> + unsigned long pfn;
> + pte_t *kpte;
> +
> + kpte = lookup_address(vaddr, &level);
> + if (!kpte || pte_none(*kpte))
> + return;
> +
> + switch (level) {
> + case PG_LEVEL_4K:
> + pfn = pte_pfn(*kpte);
> + break;
> + case PG_LEVEL_2M:
> + pfn = pmd_pfn(*(pmd_t *)kpte);
> + break;
> + case PG_LEVEL_1G:
> + pfn = pud_pfn(*(pud_t *)kpte);
> + break;
> + default:
> + return;
> + }
> +
> + psize = page_level_size(level);
> + pmask = page_level_mask(level);
> +
> + if (x86_platform.hyper.sev_migration_hcall)
> + x86_platform.hyper.sev_migration_hcall(pfn << PAGE_SHIFT,
> + psize >> PAGE_SHIFT,
> + enc);
Why do you need two indirections? One via pv.mmu_ops and then another
via x86_platform.hyper? Isn't one enough?
And if x86_platform.hyper.sev_migration_hcall isn't set the whole loop
is basically a nop.
> + vaddr_next = (vaddr & pmask) + psize;
> + }
> +}
> +
> static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
> {
> pgprot_t old_prot, new_prot;
> @@ -253,12 +297,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
> static int __init early_set_memory_enc_dec(unsigned long vaddr,
> unsigned long size, bool enc)
> {
> - unsigned long vaddr_end, vaddr_next;
> + unsigned long vaddr_end, vaddr_next, start;
> unsigned long psize, pmask;
> int split_page_size_mask;
> int level, ret;
> pte_t *kpte;
>
> + start = vaddr;
> vaddr_next = vaddr;
> vaddr_end = vaddr + size;
>
> @@ -313,6 +358,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
>
> ret = 0;
>
> + set_memory_enc_dec_hypercall(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
> + enc);
> out:
> __flush_tlb_all();
> return ret;
> @@ -451,6 +498,15 @@ void __init mem_encrypt_init(void)
> if (sev_active())
> static_branch_enable(&sev_enable_key);
>
> +#ifdef CONFIG_PARAVIRT
> + /*
> + * With SEV, we need to make a hypercall when page encryption state is
> + * changed.
> + */
> + if (sev_active())
> + pv_ops.mmu.page_encryption_changed = set_memory_enc_dec_hypercall;
> +#endif
> +
> pr_info("AMD %s active\n",
> sev_active() ? "Secure Encrypted Virtualization (SEV)"
> : "Secure Memory Encryption (SME)");
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 59eca6a94ce7..9aaf1b6f5a1b 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -27,6 +27,7 @@
> #include <asm/proto.h>
> #include <asm/memtype.h>
> #include <asm/set_memory.h>
> +#include <asm/paravirt.h>
>
> #include "../mm_internal.h"
>
> @@ -2003,6 +2004,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
> */
> cpa_flush(&cpa, 0);
>
> + /* Notify hypervisor that a given memory range is mapped encrypted
> + * or decrypted. The hypervisor will use this information during the
> + * VM migration.
> + */
> + page_encryption_changed(addr, numpages, enc);
Is this operation really so performance critical that a pv-op is
needed? Wouldn't a static key be sufficient here?
> +
> return ret;
> }
>
>
Juergen
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