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Message-ID: <ZHZGkulyli8MvXRR@aschofie-mobl2>
Date: Tue, 30 May 2023 11:55:14 -0700
From: Alison Schofield <alison.schofield@...el.com>
To: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86/sev: Move sev_setup_arch() to mem_encrypt.c
On Tue, May 30, 2023 at 03:17:28PM +0300, Alexander Shishkin wrote:
> Since commit 4d96f9109109b ("x86/sev: Replace occurrences of
> sev_active() with cc_platform_has()"), the SWIOTLB bounce buffer size
> adjustment and restricted virtio memory setting also inadvertently apply
> to TDX, which just happens to be what we want.
Hi Alexander,
Can you offer more context on how this inadvertently applies?
One bit below...
>
> To reflect this, move the corresponding code to generic mem_encrypt.c.
> No functional changes intended.
>
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> ---
> arch/x86/include/asm/mem_encrypt.h | 11 ++++++++--
> arch/x86/kernel/setup.c | 2 +-
> arch/x86/mm/mem_encrypt.c | 34 ++++++++++++++++++++++++++++++
> arch/x86/mm/mem_encrypt_amd.c | 34 ------------------------------
> 4 files changed, 44 insertions(+), 37 deletions(-)
>
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index b7126701574c..4283063c1e1c 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -37,7 +37,6 @@ void __init sme_map_bootdata(char *real_mode_data);
> void __init sme_unmap_bootdata(char *real_mode_data);
>
> void __init sme_early_init(void);
> -void __init sev_setup_arch(void);
>
> void __init sme_encrypt_kernel(struct boot_params *bp);
> void __init sme_enable(struct boot_params *bp);
> @@ -67,7 +66,6 @@ static inline void __init sme_map_bootdata(char *real_mode_data) { }
> static inline void __init sme_unmap_bootdata(char *real_mode_data) { }
>
> static inline void __init sme_early_init(void) { }
> -static inline void __init sev_setup_arch(void) { }
>
> static inline void __init sme_encrypt_kernel(struct boot_params *bp) { }
> static inline void __init sme_enable(struct boot_params *bp) { }
> @@ -92,6 +90,15 @@ void __init mem_encrypt_init(void);
>
> void add_encrypt_protection_map(void);
>
> +#ifdef CONFIG_X86_MEM_ENCRYPT
> +
> +void __init mem_encrypt_setup_arch(void);
> +
> +#else /* !CONFIG_X86_MEM_ENCRYPT */
> +
> +static inline void __init mem_encrypt_setup_arch(void) { }
> +
> +#endif /* CONFIG_X86_MEM_ENCRYPT */
> /*
> * The __sme_pa() and __sme_pa_nodebug() macros are meant for use when
> * writing to or comparing values from the cr3 register. Having the
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 16babff771bd..e2aa1d5b37a9 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1121,7 +1121,7 @@ void __init setup_arch(char **cmdline_p)
> * Needs to run after memblock setup because it needs the physical
> * memory size.
> */
> - sev_setup_arch();
> + mem_encrypt_setup_arch();
>
> efi_fake_memmap();
> efi_find_mirror();
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 9f27e14e185f..c290c55b632b 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -12,6 +12,7 @@
> #include <linux/swiotlb.h>
> #include <linux/cc_platform.h>
> #include <linux/mem_encrypt.h>
> +#include <linux/virtio_anchor.h>
It looks like this #include can be removed from mem_encrypt_amd.c
Alison
>
> /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
> bool force_dma_unencrypted(struct device *dev)
> @@ -86,3 +87,36 @@ void __init mem_encrypt_init(void)
>
> print_mem_encrypt_feature_info();
> }
> +
> +void __init mem_encrypt_setup_arch(void)
> +{
> + phys_addr_t total_mem = memblock_phys_mem_size();
> + unsigned long size;
> +
> + if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
> + return;
> +
> + /*
> + * For SEV and TDX, all DMA has to occur via shared/unencrypted pages.
> + * Kernel uses SWIOTLB to make this happen without changing device
> + * drivers. However, depending on the workload being run, the
> + * default 64MB of SWIOTLB may not be enough and SWIOTLB may
> + * run out of buffers for DMA, resulting in I/O errors and/or
> + * performance degradation especially with high I/O workloads.
> + *
> + * Adjust the default size of SWIOTLB using a percentage of guest
> + * memory for SWIOTLB buffers. Also, as the SWIOTLB bounce buffer
> + * memory is allocated from low memory, ensure that the adjusted size
> + * is within the limits of low available memory.
> + *
> + * The percentage of guest memory used here for SWIOTLB buffers
> + * is more of an approximation of the static adjustment which
> + * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
> + */
> + size = total_mem * 6 / 100;
> + size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
> + swiotlb_adjust_size(size);
> +
> + /* Set restricted memory access for virtio. */
> + virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
> +}
> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
> index e0b51c09109f..3b95e6fdf160 100644
> --- a/arch/x86/mm/mem_encrypt_amd.c
> +++ b/arch/x86/mm/mem_encrypt_amd.c
> @@ -215,40 +215,6 @@ void __init sme_map_bootdata(char *real_mode_data)
> __sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, true);
> }
>
> -void __init sev_setup_arch(void)
> -{
> - phys_addr_t total_mem = memblock_phys_mem_size();
> - unsigned long size;
> -
> - if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
> - return;
> -
> - /*
> - * For SEV, all DMA has to occur via shared/unencrypted pages.
> - * SEV uses SWIOTLB to make this happen without changing device
> - * drivers. However, depending on the workload being run, the
> - * default 64MB of SWIOTLB may not be enough and SWIOTLB may
> - * run out of buffers for DMA, resulting in I/O errors and/or
> - * performance degradation especially with high I/O workloads.
> - *
> - * Adjust the default size of SWIOTLB for SEV guests using
> - * a percentage of guest memory for SWIOTLB buffers.
> - * Also, as the SWIOTLB bounce buffer memory is allocated
> - * from low memory, ensure that the adjusted size is within
> - * the limits of low available memory.
> - *
> - * The percentage of guest memory used here for SWIOTLB buffers
> - * is more of an approximation of the static adjustment which
> - * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
> - */
> - size = total_mem * 6 / 100;
> - size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
> - swiotlb_adjust_size(size);
> -
> - /* Set restricted memory access for virtio. */
> - virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
> -}
> -
> static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
> {
> unsigned long pfn = 0;
> --
> 2.39.2
>
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