Messages in this thread | | | Date | Wed, 8 Feb 2023 16:30:16 +0000 | Subject | Re: [PATCH RFC v7 16/64] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction | From | Liam Merwick <> |
| |
On 14/12/2022 19:40, Michael Roth wrote: > From: Brijesh Singh <brijesh.singh@amd.com> > > 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@amd.com> > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > [mdr: add RMPUPDATE retry logic for transient FAIL_OVERLAP errors] > Signed-off-by: Michael Roth <michael.roth@amd.com> > --- > 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; > +}
| |