[PATCH 05/11] x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0
From: Tom Lendacky
Date: Fri Jan 26 2024 - 17:18:20 EST
The PVALIDATE instruction can only be performed at VMPL0. An SVSM will
be present when running at VMPL1 or a lower privilege level.
When an SVSM is present, use the SVSM_CORE_PVALIDATE call to perform
memory validation instead of issuing the PVALIDATE instruction directly.
The validation of a single 4K page is now explicitly identified as such
in the function name, pvalidate_4k_page(). The pvalidate_pages() function
is used for validating 1 or more pages at either 4K or 2M in size. Each
function, however, determines whether it can issue the PVALIDATE directly
or whether the SVSM needs to be invoked.
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
arch/x86/boot/compressed/sev.c | 42 +++++++-
arch/x86/include/asm/sev.h | 22 +++++
arch/x86/kernel/sev-shared.c | 176 ++++++++++++++++++++++++++++++++-
arch/x86/kernel/sev.c | 25 +++--
4 files changed, 247 insertions(+), 18 deletions(-)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 5d2403914ceb..3fbb614c31e0 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -38,6 +38,16 @@ static u8 vmpl __section(".data");
static u64 boot_svsm_caa_pa __section(".data");
static struct svsm_ca *boot_svsm_caa __section(".data");
+static struct svsm_ca *__svsm_get_caa(void)
+{
+ return boot_svsm_caa;
+}
+
+static u64 __svsm_get_caa_pa(void)
+{
+ return boot_svsm_caa_pa;
+}
+
/*
* Copy a version of this function here - insn-eval.c can't be used in
* pre-decompression code.
@@ -135,6 +145,24 @@ static bool fault_in_kernel_space(unsigned long address)
/* Include code for early handlers */
#include "../../kernel/sev-shared.c"
+static int svsm_protocol(struct svsm_call *call)
+{
+ struct ghcb *ghcb;
+ int ret;
+
+ if (boot_ghcb)
+ ghcb = boot_ghcb;
+ else
+ ghcb = NULL;
+
+ do {
+ ret = ghcb ? __svsm_ghcb_protocol(ghcb, call)
+ : __svsm_msr_protocol(call);
+ } while (ret == SVSM_ERR_BUSY);
+
+ return ret;
+}
+
bool sev_snp_enabled(void)
{
return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
@@ -151,8 +179,8 @@ static void __page_state_change(unsigned long paddr, enum psc_op op)
* If private -> shared then invalidate the page before requesting the
* state change in the RMP table.
*/
- if (op == SNP_PAGE_STATE_SHARED && pvalidate(paddr, RMP_PG_SIZE_4K, 0))
- sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
+ if (op == SNP_PAGE_STATE_SHARED)
+ pvalidate_4k_page(paddr, paddr, 0);
/* Issue VMGEXIT to change the page state in RMP table. */
sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op));
@@ -167,8 +195,8 @@ static void __page_state_change(unsigned long paddr, enum psc_op op)
* 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(paddr, RMP_PG_SIZE_4K, 1))
- sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
+ if (op == SNP_PAGE_STATE_PRIVATE)
+ pvalidate_4k_page(paddr, paddr, 1);
}
void snp_set_page_private(unsigned long paddr)
@@ -261,6 +289,12 @@ void sev_es_shutdown_ghcb(void)
if (!sev_es_check_cpu_features())
error("SEV-ES CPU Features missing.");
+ /*
+ * Ensure that the boot GHCB isn't used for the PVALIDATE when running
+ * under an SVSM.
+ */
+ boot_ghcb = NULL;
+
/*
* GHCB Page must be flushed from the cache and mapped encrypted again.
* Otherwise the running kernel will see strange cache effects when
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 2f1e583769fc..dbd7fd041689 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -172,6 +172,27 @@ struct svsm_ca {
#define SVSM_ERR_INVALID_PARAMETER 0x80000005
#define SVSM_ERR_INVALID_REQUEST 0x80000006
#define SVSM_ERR_BUSY 0x80000007
+#define SVSM_PVALIDATE_FAIL_SIZEMISMATCH 0x80001006
+
+/*
+ * The SVSM PVALIDATE related structures
+ */
+struct svsm_pvalidate_entry {
+ u64 page_size : 2,
+ action : 1,
+ ignore_cf : 1,
+ rsvd : 8,
+ pfn : 52;
+};
+
+struct svsm_pvalidate_call {
+ u16 entries;
+ u16 next;
+
+ u8 rsvd1[4];
+
+ struct svsm_pvalidate_entry entry[];
+};
/*
* SVSM protocol structure
@@ -192,6 +213,7 @@ struct svsm_call {
#define SVSM_CORE_CALL(x) ((0ULL << 32) | (x))
#define SVSM_CORE_REMAP_CA 0
+#define SVSM_CORE_PVALIDATE 1
#ifdef CONFIG_AMD_MEM_ENCRYPT
extern void __sev_es_ist_enter(struct pt_regs *regs);
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 7e9fa5d8889b..f26e872bc5d0 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -81,6 +81,8 @@ static u32 cpuid_std_range_max __ro_after_init;
static u32 cpuid_hyp_range_max __ro_after_init;
static u32 cpuid_ext_range_max __ro_after_init;
+static int svsm_protocol(struct svsm_call *call);
+
static bool __init sev_es_check_cpu_features(void)
{
if (!has_cpuflag(X86_FEATURE_RDRAND)) {
@@ -1181,7 +1183,65 @@ static void __init setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
}
}
-static void pvalidate_pages(struct snp_psc_desc *desc)
+static int base_pvalidate_4k_page(unsigned long vaddr, bool validate)
+{
+ return pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
+}
+
+static int svsm_pvalidate_4k_page(unsigned long paddr, bool validate)
+{
+ struct svsm_pvalidate_call *pvalidate_call;
+ struct svsm_call call = {};
+ u64 pvalidate_call_pa;
+ unsigned long flags;
+ int ret;
+
+ /*
+ * This can be called very early in the boot, use native functions in
+ * order to avoid paravirt issues.
+ */
+ flags = native_save_fl();
+ if (flags & X86_EFLAGS_IF)
+ native_irq_disable();
+
+ call.caa = __svsm_get_caa();
+
+ pvalidate_call = (struct svsm_pvalidate_call *)call.caa->svsm_buffer;
+ pvalidate_call_pa = __svsm_get_caa_pa() + offsetof(struct svsm_ca, svsm_buffer);
+
+ pvalidate_call->entries = 1;
+ pvalidate_call->next = 0;
+ pvalidate_call->entry[0].page_size = RMP_PG_SIZE_4K;
+ pvalidate_call->entry[0].action = validate;
+ pvalidate_call->entry[0].ignore_cf = 0;
+ pvalidate_call->entry[0].pfn = paddr >> PAGE_SHIFT;
+
+ /* Protocol 0, Call ID 1 */
+ call.rax = SVSM_CORE_CALL(SVSM_CORE_PVALIDATE);
+ call.rcx = pvalidate_call_pa;
+
+ ret = svsm_protocol(&call);
+
+ if (flags & X86_EFLAGS_IF)
+ native_irq_enable();
+
+ return ret;
+}
+
+static void pvalidate_4k_page(unsigned long vaddr, unsigned long paddr, bool validate)
+{
+ int ret;
+
+ ret = vmpl ? svsm_pvalidate_4k_page(paddr, validate)
+ : base_pvalidate_4k_page(vaddr, validate);
+
+ if (ret) {
+ WARN(1, "Failed to validate address 0x%lx ret %d", vaddr, ret);
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
+ }
+}
+
+static void base_pvalidate_pages(struct snp_psc_desc *desc)
{
struct psc_entry *e;
unsigned long vaddr;
@@ -1215,6 +1275,120 @@ static void pvalidate_pages(struct snp_psc_desc *desc)
}
}
+static void svsm_pvalidate_pages(struct snp_psc_desc *desc)
+{
+ struct svsm_pvalidate_call *pvalidate_call;
+ struct svsm_pvalidate_entry *pe;
+ unsigned int call_count, i;
+ struct svsm_call call = {};
+ u64 pvalidate_call_pa;
+ struct psc_entry *e;
+ unsigned long flags;
+ unsigned long vaddr;
+ bool action;
+ int ret;
+
+ /*
+ * This can be called very early in the boot, use native functions in
+ * order to avoid paravirt issues.
+ */
+ flags = native_save_fl();
+ if (flags & X86_EFLAGS_IF)
+ native_irq_disable();
+
+ call.caa = __svsm_get_caa();
+
+ pvalidate_call = (struct svsm_pvalidate_call *)call.caa->svsm_buffer;
+ pvalidate_call_pa = __svsm_get_caa_pa() + offsetof(struct svsm_ca, svsm_buffer);
+
+ /* Calculate how many entries the CA buffer can hold */
+ call_count = sizeof(call.caa->svsm_buffer);
+ call_count -= offsetof(struct svsm_pvalidate_call, entry);
+ call_count /= sizeof(pvalidate_call->entry[0]);
+
+ /* Protocol 0, Call ID 1 */
+ call.rax = SVSM_CORE_CALL(SVSM_CORE_PVALIDATE);
+ call.rcx = pvalidate_call_pa;
+
+ pvalidate_call->entries = 0;
+ pvalidate_call->next = 0;
+
+ for (i = 0; i <= desc->hdr.end_entry; i++) {
+ e = &desc->entries[i];
+ pe = &pvalidate_call->entry[pvalidate_call->entries];
+
+ pe->page_size = e->pagesize ? RMP_PG_SIZE_2M : RMP_PG_SIZE_4K;
+ pe->action = e->operation == SNP_PAGE_STATE_PRIVATE;
+ pe->ignore_cf = 0;
+ pe->pfn = e->gfn;
+
+ pvalidate_call->entries++;
+ if (pvalidate_call->entries < call_count && i != desc->hdr.end_entry)
+ continue;
+
+ ret = svsm_protocol(&call);
+ if (ret == SVSM_PVALIDATE_FAIL_SIZEMISMATCH &&
+ pvalidate_call->entry[pvalidate_call->next].page_size == RMP_PG_SIZE_2M) {
+ u64 pfn, pfn_end;
+
+ /*
+ * The "next" field is the index of the failed entry. Calculate the
+ * index of the entry after the failed entry before the fields are
+ * cleared so that processing can continue on from that point (take
+ * into account the for loop adding 1 to the entry).
+ */
+ i -= pvalidate_call->entries - pvalidate_call->next;
+ i += 1;
+
+ action = pvalidate_call->entry[pvalidate_call->next].action;
+ pfn = pvalidate_call->entry[pvalidate_call->next].pfn;
+ pfn_end = pfn + 511;
+
+ pvalidate_call->entries = 0;
+ pvalidate_call->next = 0;
+ for (; pfn <= pfn_end; pfn++) {
+ pe = &pvalidate_call->entry[pvalidate_call->entries];
+
+ pe->page_size = RMP_PG_SIZE_4K;
+ pe->action = action;
+ pe->ignore_cf = 0;
+ pe->pfn = pfn;
+
+ pvalidate_call->entries++;
+ if (pvalidate_call->entries < call_count && pfn != pfn_end)
+ continue;
+
+ ret = svsm_protocol(&call);
+ if (ret != SVSM_SUCCESS)
+ break;
+
+ pvalidate_call->entries = 0;
+ pvalidate_call->next = 0;
+ }
+ }
+
+ if (ret != SVSM_SUCCESS) {
+ pe = &pvalidate_call->entry[pvalidate_call->next];
+ vaddr = (unsigned long)pfn_to_kaddr(pe->pfn);
+
+ WARN(1, "Failed to validate address %lx ret=%#x (%d)", vaddr, ret, ret);
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
+ }
+
+ pvalidate_call->entries = 0;
+ pvalidate_call->next = 0;
+ }
+
+ if (flags & X86_EFLAGS_IF)
+ native_irq_enable();
+}
+
+static void pvalidate_pages(struct snp_psc_desc *desc)
+{
+ vmpl ? svsm_pvalidate_pages(desc)
+ : base_pvalidate_pages(desc);
+}
+
static int vmgexit_psc(struct ghcb *ghcb, struct snp_psc_desc *desc)
{
int cur_entry, end_entry, ret = 0;
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 3bd7860fbfe1..2fd21090ef6b 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -161,6 +161,12 @@ static struct svsm_ca *__svsm_get_caa(void)
: boot_svsm_caa;
}
+static u64 __svsm_get_caa_pa(void)
+{
+ return sev_cfg.cas_initialized ? this_cpu_read(svsm_caa_pa)
+ : boot_svsm_caa_pa;
+}
+
static __always_inline bool on_vc_stack(struct pt_regs *regs)
{
unsigned long sp = regs->sp;
@@ -777,7 +783,6 @@ static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
{
unsigned long paddr_end;
u64 val;
- int ret;
vaddr = vaddr & PAGE_MASK;
@@ -785,12 +790,9 @@ static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
paddr_end = paddr + (npages << PAGE_SHIFT);
while (paddr < paddr_end) {
- if (op == SNP_PAGE_STATE_SHARED) {
- /* Page validation must be rescinded before changing to shared */
- ret = pvalidate(vaddr, RMP_PG_SIZE_4K, false);
- if (WARN(ret, "Failed to validate address 0x%lx ret %d", paddr, ret))
- goto e_term;
- }
+ /* 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
@@ -812,12 +814,9 @@ static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
paddr, GHCB_MSR_PSC_RESP_VAL(val)))
goto e_term;
- if (op == SNP_PAGE_STATE_PRIVATE) {
- /* Page validation must be performed after changing to private */
- ret = pvalidate(vaddr, RMP_PG_SIZE_4K, true);
- if (WARN(ret, "Failed to validate address 0x%lx ret %d", paddr, ret))
- goto e_term;
- }
+ /* Page validation must be performed after changing to private */
+ if (op == SNP_PAGE_STATE_PRIVATE)
+ pvalidate_4k_page(vaddr, paddr, true);
vaddr += PAGE_SIZE;
paddr += PAGE_SIZE;
--
2.42.0