KVM: x86: Use a proper bitmap for tracking available/dirty registers

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Define regs_{avail,dirty} as bitmaps instead of U32s to harden against
overflow, and to allow for dynamically sizing the bitmaps when APX comes
along, which will add 16 more GPRs (R16-R31) and thus increase the total
number of registers beyond 32.

Open code writes in the "reset" APIs, as the writes are hot paths and
bitmap_write() is complete overkill for what KVM needs.  Even better,
hardcoding writes to entry '0' in the array is a perfect excuse to assert
that the array contains exactly one entry, e.g. to effectively add guard
against defining R16-R31 in 32-bit kernels.

For all intents and purposes, no functional change intended even though
using bitmap_fill() will mean "undefined" registers are no longer marked
available and dirty (KVM should never be querying those bits).

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Message-ID: <20260409224236.2021562-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Sean Christopherson 2026-04-09 15:42:35 -07:00 • committed by Paolo Bonzini

parent 133ecccbfe

commit 39a5ee37be

3 changed files with 18 additions and 12 deletions

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6

arch/x86/include/asm/kvm_host.h

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20

arch/x86/kvm/kvm_cache_regs.h

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4

arch/x86/kvm/x86.c

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