From: Ard Biesheuvel Date: Thu, 28 Aug 2025 10:22:10 +0000 (+0200) Subject: x86/sev: Share implementation of MSR-based page state change X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d5949ea50c5642ab7e3c4dd6020e23725c079b25;p=users%2Fhch%2Fmisc.git x86/sev: Share implementation of MSR-based page state change Both the decompressor and the SEV startup code implement the exact same sequence for invoking the MSR based communication protocol to effectuate a page state change. Before tweaking the internal APIs used in both versions, merge them and share them so those tweaks are only needed in a single place. Signed-off-by: Ard Biesheuvel Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/20250828102202.1849035-31-ardb+git@google.com --- diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c index f2b8dfbd453c..6b62c75ea911 100644 --- a/arch/x86/boot/compressed/sev.c +++ b/arch/x86/boot/compressed/sev.c @@ -60,46 +60,12 @@ static bool sev_snp_enabled(void) return sev_status & MSR_AMD64_SEV_SNP_ENABLED; } -static void __page_state_change(unsigned long paddr, enum psc_op op) -{ - u64 val, msr; - - /* - * If private -> shared then invalidate the page before requesting the - * state change in the RMP table. - */ - 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(); - - /* Read the response of the VMGEXIT. */ - val = sev_es_rd_ghcb_msr(); - 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. - */ - if (op == SNP_PAGE_STATE_PRIVATE) - pvalidate_4k_page(paddr, paddr, true); -} - void snp_set_page_private(unsigned long paddr) { if (!sev_snp_enabled()) return; - __page_state_change(paddr, SNP_PAGE_STATE_PRIVATE); + __page_state_change(paddr, paddr, SNP_PAGE_STATE_PRIVATE); } void snp_set_page_shared(unsigned long paddr) @@ -107,7 +73,7 @@ void snp_set_page_shared(unsigned long paddr) if (!sev_snp_enabled()) return; - __page_state_change(paddr, SNP_PAGE_STATE_SHARED); + __page_state_change(paddr, paddr, SNP_PAGE_STATE_SHARED); } bool early_setup_ghcb(void) @@ -133,7 +99,7 @@ bool early_setup_ghcb(void) void snp_accept_memory(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); + __page_state_change(pa, pa, SNP_PAGE_STATE_PRIVATE); } void sev_es_shutdown_ghcb(void) diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c index 80d4fdada33a..00220d7b981b 100644 --- a/arch/x86/boot/startup/sev-shared.c +++ b/arch/x86/boot/startup/sev-shared.c @@ -664,6 +664,41 @@ static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr, sev_evict_cache((void *)vaddr, 1); } +static void __head __page_state_change(unsigned long vaddr, unsigned long paddr, + enum psc_op op) +{ + u64 val, msr; + + /* + * If private -> shared then invalidate the page before requesting the + * state change in the RMP table. + */ + if (op == SNP_PAGE_STATE_SHARED) + pvalidate_4k_page(vaddr, 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(); + + /* Read the response of the VMGEXIT. */ + val = sev_es_rd_ghcb_msr(); + 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. + */ + if (op == SNP_PAGE_STATE_PRIVATE) + pvalidate_4k_page(vaddr, paddr, true); +} + /* * Maintain the GPA of the SVSM Calling Area (CA) in order to utilize the SVSM * services needed when not running in VMPL0. diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c index 8a06f6026101..5eb7d939ebd3 100644 --- a/arch/x86/boot/startup/sev-startup.c +++ b/arch/x86/boot/startup/sev-startup.c @@ -135,7 +135,6 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr, unsigned long npages, enum psc_op op) { unsigned long paddr_end; - u64 val; vaddr = vaddr & PAGE_MASK; @@ -143,37 +142,11 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr, paddr_end = paddr + (npages << PAGE_SHIFT); while (paddr < paddr_end) { - /* Page validation must be rescinded before changing to shared */ - if (op == SNP_PAGE_STATE_SHARED) - pvalidate_4k_page(vaddr, paddr, false); - - /* - * Use the MSR protocol because this function can be called before - * the GHCB is established. - */ - sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op)); - VMGEXIT(); - - val = sev_es_rd_ghcb_msr(); - - if (GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP) - goto e_term; - - if (GHCB_MSR_PSC_RESP_VAL(val)) - goto e_term; - - /* Page validation must be performed after changing to private */ - if (op == SNP_PAGE_STATE_PRIVATE) - pvalidate_4k_page(vaddr, paddr, true); + __page_state_change(vaddr, paddr, op); vaddr += PAGE_SIZE; paddr += PAGE_SIZE; } - - return; - -e_term: - sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC); } void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,