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Fri, 04 Apr 2025 01:29:35 -0700 (PDT) Date: Fri, 4 Apr 2025 10:29:25 +0200 In-Reply-To: <20250404082921.2767593-5-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250404082921.2767593-5-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=4109; i=ardb@kernel.org; h=from:subject; bh=gU6xURlLYFEx9EzfjM9uVyI6mnhjSldn1tb1ZweMrPM=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIf39jNT1l+JaZF+l6cw8cmpZjmNTX6fNpFntT4UObMzSe Wa06GxfRykLgxgHg6yYIovA7L/vdp6eKFXrPEsWZg4rE8gQBi5OAZhIuAjD/8TFqiu2b/WaNXHK 90+Lm5Ne/FSrZut7m/DJ1ni+goDObQmG/76NtlWZJe/SGB9fTO440NU4Vepe8ZoDxRuF3sziCDh zjAUA X-Mailer: git-send-email 2.49.0.504.g3bcea36a83-goog Message-ID: <20250404082921.2767593-8-ardb+git@google.com> Subject: [PATCH v2 3/3] x86/boot: Implement early memory acceptance for SEV-SNP From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Ard Biesheuvel , Tom Lendacky , "Kirill A. Shutemov" , Borislav Petkov , Dionna Amalie Glaze , Kevin Loughlin From: Ard Biesheuvel Switch to a different API for accepting memory in SEV-SNP guests, one which is actually supported at the point during boot where the EFI stub may need to accept memory, but the SEV-SNP init code has not executed yet. Co-developed-by: Tom Lendacky Signed-off-by: Tom Lendacky Signed-off-by: Ard Biesheuvel --- arch/x86/boot/compressed/sev.c | 34 +++++++++++++++++--- drivers/firmware/efi/libstub/x86-stub.c | 4 ++- 2 files changed, 33 insertions(+), 5 deletions(-) diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c index bb55934c1cee..88100bf83ded 100644 --- a/arch/x86/boot/compressed/sev.c +++ b/arch/x86/boot/compressed/sev.c @@ -164,10 +164,7 @@ bool sev_snp_enabled(void) static void __page_state_change(unsigned long paddr, enum psc_op op) { - u64 val; - - if (!sev_snp_enabled()) - return; + u64 val, msr; /* * If private -> shared then invalidate the page before requesting the @@ -176,6 +173,9 @@ static void __page_state_change(unsigned long paddr, enum psc_op op) if (op == SNP_PAGE_STATE_SHARED) pvalidate_4k_page(paddr, paddr, false); + /* Save the current GHCB MSR value */ + msr = sev_es_rd_ghcb_msr(); + /* Issue VMGEXIT to change the page state in RMP table. */ sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op)); VMGEXIT(); @@ -185,6 +185,9 @@ static void __page_state_change(unsigned long paddr, enum psc_op op) if ((GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP) || GHCB_MSR_PSC_RESP_VAL(val)) sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC); + /* Restore the GHCB MSR value */ + sev_es_wr_ghcb_msr(msr); + /* * Now that page state is changed in the RMP table, validate it so that it is * consistent with the RMP entry. @@ -195,11 +198,17 @@ static void __page_state_change(unsigned long paddr, enum psc_op op) void snp_set_page_private(unsigned long paddr) { + if (!sev_snp_enabled()) + return; + __page_state_change(paddr, SNP_PAGE_STATE_PRIVATE); } void snp_set_page_shared(unsigned long paddr) { + if (!sev_snp_enabled()) + return; + __page_state_change(paddr, SNP_PAGE_STATE_SHARED); } @@ -261,6 +270,11 @@ static phys_addr_t __snp_accept_memory(struct snp_psc_desc *desc, return pa; } +/* + * The memory acceptance support uses the boot GHCB page to perform + * the required page state change operation before validating the + * pages. + */ void snp_accept_memory(phys_addr_t start, phys_addr_t end) { struct snp_psc_desc desc = {}; @@ -275,6 +289,18 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end) pa = __snp_accept_memory(&desc, pa, end); } +/* + * The early version of memory acceptance is needed when being called + * from the EFI stub driver. The pagetable manipulation to mark the + * boot GHCB page as shared can't be performed at this stage, so use + * the GHCB page state change MSR protocol instead. + */ +void snp_accept_memory_early(phys_addr_t start, phys_addr_t end) +{ + for (phys_addr_t pa = start; pa < end; pa += PAGE_SIZE) + __page_state_change(pa, SNP_PAGE_STATE_PRIVATE); +} + void sev_es_shutdown_ghcb(void) { if (!boot_ghcb) diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index 7d9cf473f4d0..dcf436dea99e 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -383,6 +383,8 @@ static bool efistub_is_sevsnp_guest(void) return sev_get_status() & MSR_AMD64_SEV_SNP_ENABLED; } +void snp_accept_memory_early(phys_addr_t start, phys_addr_t end); + void efistub_accept_memory(phys_addr_t start, phys_addr_t end) { static bool once, is_tdx, is_sevsnp; @@ -398,7 +400,7 @@ void efistub_accept_memory(phys_addr_t start, phys_addr_t end) if (is_tdx) tdx_accept_memory(start, end); else if (is_sevsnp) - snp_accept_memory(start, end); + snp_accept_memory_early(start, end); } #endif