On 14/12/2022 19:40, Michael Roth wrote:
From: Brijesh Singh <brijesh.singh@xxxxxxx>
The RMPUPDATE instruction writes a new RMP entry in the RMP Table. The
hypervisor will use the instruction to add pages to the RMP table. See
APM3 for details on the instruction operations.
The PSMASH instruction expands a 2MB RMP entry into a corresponding set
of contiguous 4KB-Page RMP entries. The hypervisor will use this
instruction to adjust the RMP entry without invalidating the previous
RMP entry.
Add the following external interface API functions:
int psmash(u64 pfn);
psmash is used to smash a 2MB aligned page into 4K
pages while preserving the Validated bit in the RMP.
int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
Used to assign a page to guest using the RMPUPDATE instruction.
int rmp_make_shared(u64 pfn, enum pg_level level);
Used to transition a page to hypervisor/shared state using the RMPUPDATE instruction.
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
[mdr: add RMPUPDATE retry logic for transient FAIL_OVERLAP errors]
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
arch/x86/include/asm/sev.h | 24 ++++++++++
arch/x86/kernel/sev.c | 95 ++++++++++++++++++++++++++++++++++++++
2 files changed, 119 insertions(+)
...
+
+static int rmpupdate(u64 pfn, struct rmp_state *val)
+{
+ unsigned long paddr = pfn << PAGE_SHIFT;
+ int retries = 0;
+ int ret;
+
+ if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+ return -ENXIO;
+
+retry:
+ /* Binutils version 2.36 supports the RMPUPDATE mnemonic. */
+ asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE"
+ : "=a"(ret)
+ : "a"(paddr), "c"((unsigned long)val)
+ : "memory", "cc");
+
+ if (ret) {
+ if (!retries) {
+ pr_err("RMPUPDATE failed, ret: %d, pfn: %llx, npages: %d, level: %d, retrying (max: %d)...\n",
+ ret, pfn, npages, level, 2 * num_present_cpus());
This patch isn't bisectable - 'npages' isn't defined in this patch -
it's defined later in Patch18
otherwise LGTM
Regards,
Liam
+ dump_stack();
+ }
+ retries++;
+ if (retries < 2 * num_present_cpus())
+ goto retry;
+ } else if (retries > 0) {
+ pr_err("RMPUPDATE for pfn %llx succeeded after %d retries\n", pfn, retries);
+ }
+
+ return ret;
+}
