From: Juergen Gross <jgr...@suse.com> Sent: Tuesday, May 6, 2025 2:20 AM > > When building a kernel with CONFIG_PARAVIRT_XXL the paravirt > infrastructure will always use functions for reading or writing MSRs, > even when running on bare metal. > > Switch to inline RDMSR/WRMSR instructions in this case, reducing the > paravirt overhead. > > In order to make this less intrusive, some further reorganization of > the MSR access helpers is done in the first 4 patches. > > This series has been tested to work with Xen PV and on bare metal.
I've tested in SEV-SNP and TDX guests with paravisor on Hyper-V. Basic smoke test showed no issues. Tested-by: Michael Kelley <mhkli...@outlook.com> > > There has been another approach by Xin Li, which used dedicated #ifdef > and removing the MSR related paravirt hooks instead of just modifying > the paravirt code generation. > > Please note that I haven't included the use of WRMSRNS or the > immediate forms of WRMSR and RDMSR, because I wanted to get some > feedback on my approach first. Enhancing paravirt for those cases > is not very complicated, as the main base is already prepared for > that enhancement. > > This series is based on the x86/msr branch of the tip tree. > > Juergen Gross (6): > coco/tdx: Rename MSR access helpers > x86/kvm: Rename the KVM private read_msr() function > x86/msr: minimize usage of native_*() msr access functions > x86/msr: Move MSR trace calls one function level up > x86/paravirt: Switch MSR access pv_ops functions to instruction > interfaces > x86/msr: reduce number of low level MSR access helpers > > arch/x86/coco/tdx/tdx.c | 8 +- > arch/x86/hyperv/ivm.c | 2 +- > arch/x86/include/asm/kvm_host.h | 2 +- > arch/x86/include/asm/msr.h | 116 ++++++++++------- > arch/x86/include/asm/paravirt.h | 152 ++++++++++++++-------- > arch/x86/include/asm/paravirt_types.h | 13 +- > arch/x86/include/asm/qspinlock_paravirt.h | 5 +- > arch/x86/kernel/kvmclock.c | 2 +- > arch/x86/kernel/paravirt.c | 26 +++- > arch/x86/kvm/svm/svm.c | 16 +-- > arch/x86/kvm/vmx/vmx.c | 4 +- > arch/x86/xen/enlighten_pv.c | 60 ++++++--- > arch/x86/xen/pmu.c | 4 +- > 13 files changed, 262 insertions(+), 148 deletions(-) > > -- > 2.43.0 >
