On Mon, Jun 10, 2024 at 12:21:03PM +0200, vsntk18@xxxxxxxxx wrote: > From: Vasant Karasulli <vkarasulli@xxxxxxx> > > Hi, > > here are changes to enable kexec/kdump in SEV-ES guests. The biggest > problem for supporting kexec/kdump under SEV-ES is to find a way to > hand the non-boot CPUs (APs) from one kernel to another. > > Without SEV-ES the first kernel parks the CPUs in a HLT loop until > they get reset by the kexec'ed kernel via an INIT-SIPI-SIPI sequence. > For virtual machines the CPU reset is emulated by the hypervisor, > which sets the vCPU registers back to reset state. > > This does not work under SEV-ES, because the hypervisor has no access > to the vCPU registers and can't make modifications to them. So an > SEV-ES guest needs to reset the vCPU itself and park it using the > AP-reset-hold protocol. Upon wakeup the guest needs to jump to > real-mode and to the reset-vector configured in the AP-Jump-Table. > > The code to do this is the main part of this patch-set. It works by > placing code on the AP Jump-Table page itself to park the vCPU and for > jumping to the reset vector upon wakeup. The code on the AP Jump Table > runs in 16-bit protected mode with segment base set to the beginning > of the page. The AP Jump-Table is usually not within the first 1MB of > memory, so the code can't run in real-mode. > > The AP Jump-Table is the best place to put the parking code, because > the memory is owned, but read-only by the firmware and writeable by > the OS. Only the first 4 bytes are used for the reset-vector, leaving > the rest of the page for code/data/stack to park a vCPU. The code > can't be in kernel memory because by the time the vCPU wakes up the > memory will be owned by the new kernel, which might have overwritten it > already. > > The other patches add initial GHCB Version 2 protocol support, because > kexec/kdump need the MSR-based (without a GHCB) AP-reset-hold VMGEXIT, > which is a GHCB protocol version 2 feature. > > The kexec'ed kernel is also entered via the decompressor and needs > MMIO support there, so this patch-set also adds MMIO #VC support to > the decompressor and support for handling CLFLUSH instructions. > > Finally there is also code to disable kexec/kdump support at runtime > when the environment does not support it (e.g. no GHCB protocol > version 2 support or AP Jump Table over 4GB). > > The diffstat looks big, but most of it is moving code for MMIO #VC > support around to make it available to the decompressor. > > The previous version of this patch-set can be found here: > > https://lore.kernel.org/kvm/20240408074049.7049-1-vsntk18@xxxxxxxxx/ > > Please review. > > Thanks, > Vasant > > Changes v5->v6: > - Rebased to v6.10-rc3 kernel > > Changes v4->v5: > - Rebased to v6.9-rc2 kernel > - Applied review comments by Tom Lendacky > - Exclude the AP jump table related code for SEV-SNP guests > > Changes v3->v4: > - Rebased to v6.8 kernel > - Applied review comments by Sean Christopherson > - Combined sev_es_setup_ap_jump_table() and sev_setup_ap_jump_table() > into a single function which makes caching jump table address > unnecessary > - annotated struct sev_ap_jump_table_header with __packed attribute > - added code to set up real mode data segment at boot time instead of > hardcoding the value. > > Joerg Roedel (9): > x86/kexec/64: Disable kexec when SEV-ES is active > x86/sev: Save and print negotiated GHCB protocol version > x86/sev: Set GHCB data structure version > x86/sev: Setup code to park APs in the AP Jump Table > x86/sev: Park APs on AP Jump Table with GHCB protocol version 2 > x86/sev: Use AP Jump Table blob to stop CPU > x86/sev: Add MMIO handling support to boot/compressed/ code > x86/sev: Handle CLFLUSH MMIO events > x86/kexec/64: Support kexec under SEV-ES with AP Jump Table Blob > > Vasant Karasulli (1): > x86/sev: Exclude AP jump table related code for SEV-SNP guests > > arch/x86/boot/compressed/sev.c | 45 +- > arch/x86/include/asm/insn-eval.h | 1 + > arch/x86/include/asm/realmode.h | 5 + > arch/x86/include/asm/sev-ap-jumptable.h | 30 + > arch/x86/include/asm/sev.h | 7 + > arch/x86/kernel/machine_kexec_64.c | 12 + > arch/x86/kernel/process.c | 8 + > arch/x86/kernel/sev-shared.c | 234 +++++- > arch/x86/kernel/sev.c | 376 +++++----- > arch/x86/lib/insn-eval-shared.c | 921 ++++++++++++++++++++++++ > arch/x86/lib/insn-eval.c | 911 +---------------------- > arch/x86/realmode/Makefile | 9 +- > arch/x86/realmode/init.c | 5 +- > arch/x86/realmode/rm/Makefile | 11 +- > arch/x86/realmode/rm/header.S | 3 + > arch/x86/realmode/rm/sev.S | 85 +++ > arch/x86/realmode/rmpiggy.S | 6 + > arch/x86/realmode/sev/Makefile | 33 + > arch/x86/realmode/sev/ap_jump_table.S | 131 ++++ > arch/x86/realmode/sev/ap_jump_table.lds | 24 + > 20 files changed, 1711 insertions(+), 1146 deletions(-) > create mode 100644 arch/x86/include/asm/sev-ap-jumptable.h > create mode 100644 arch/x86/lib/insn-eval-shared.c > create mode 100644 arch/x86/realmode/rm/sev.S > create mode 100644 arch/x86/realmode/sev/Makefile > create mode 100644 arch/x86/realmode/sev/ap_jump_table.S > create mode 100644 arch/x86/realmode/sev/ap_jump_table.lds > > > base-commit: 83a7eefedc9b56fe7bfeff13b6c7356688ffa670 > -- > 2.34.1 > > <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly. </formletter>
