cpu/vc: implement RDTSC and RDSTCP #VC handlers
#327
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p4zuu
reviewed
Apr 24, 2024
When accessing GHCB fields that were written to by the host, we must check that they are set as valid in the valid bitmap. Conversely, when setting fields of the GHCB to communicate with the host, we must set them as valid in the valid bitmap. To do so, we must get the offset of such field in the GHCB and translate it into an index into the valid bitmap. Instead of hardcoding GHCB field offsets, implement getters and setters for each field, which will automatically get or set the appropriate value from the valid bitmap based on that field's offset. This was not done before because there was no way of getting a field's offset at compile time before Rust 1.77, which introduced the core::mem::offset_of!() macro. Signed-off-by: Carlos López <carlos.lopez@suse.com>
When performing a VMGEXIT to request a RDMSR we expect the instruction results to be placed in RDX and RAX. However, we must check that the hypervisor set those registers as valid before reading them. To do so, use the recently introduced getters. Signed-off-by: Carlos López <carlos.lopez@suse.com>
Implement a the #VC handler for the SVM_RDTSC exit reason. This also requires decoding the RDTSC instruction. The handler simply forwards the call into the GHCB and copies out the relevant registers to the guest state. While we are at it, enable the relevant RDTSC #VC test. Signed-off-by: Carlos López <carlos.lopez@suse.com>
Due to a typo, this function was issuing a RDTSC instruction instead of RDTSCP. Signed-off-by: Carlos López <carlos.lopez@suse.com>
Implement a the #VC handler for the SVM_RDTSCP exit reason. This also requires decoding the RDTSCP instruction. The handler simply forwards the call into the GHCB and copies out the relevant registers to the guest state. While we are at it, enable the relevant RDTSCP #VC test. Signed-off-by: Carlos López <carlos.lopez@suse.com>
Add a test to verify that the GHCB layout is as expected, as per the GHCB specification: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf Signed-off-by: Carlos López <carlos.lopez@suse.com>
p4zuu
reviewed
Apr 24, 2024
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Well done! I especially like the new macros for GHCB getters/setters and the test-case checking the GHCB offsets. |
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offset_of!()macro).GHCB::rdmsr_regs().RDTSC#VC handler and enable relevant in-SVSM test.rdtscp().RDTSCP#VC handler and enable relevant in-SVSM test.This works towards a more complete implementation of #14 .