Commit d5949ea5 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Borislav Petkov (AMD)
Browse files

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: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-31-ardb+git@google.com
parent a5f03880

arch/x86/boot/compressed/sev.c

+3 −37
Original line number Diff line number Diff line
@@ -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)

arch/x86/boot/startup/sev-shared.c

+35 −0
Original line number Diff line number Diff line
@@ -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.

arch/x86/boot/startup/sev-startup.c

+1 −28
Original line number Diff line number Diff line
@@ -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,