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x86/sev: Share implementation of MSR-based page state change

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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 <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-31-ardb+git@google.com
This commit is contained in:
Ard Biesheuvel 2025-08-28 12:22:10 +02:00 committed by Borislav Petkov (AMD)
parent a5f03880f0
commit d5949ea50c
3 changed files with 39 additions and 65 deletions
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40
arch/x86/boot/compressed/sev.c
View File

@ -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)

35
arch/x86/boot/startup/sev-shared.c
View File

@ -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.

29
arch/x86/boot/startup/sev-startup.c
View File

@ -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,