On 05/12/20 01:48, Maciej S. Szmigiero wrote:
From: "Maciej S. Szmigiero" <maciej.szmigiero@xxxxxxxxxx>
Commit cae7ed3c2cb0 ("KVM: x86: Refactor the MMIO SPTE generation handling")
cleaned up the computation of MMIO generation SPTE masks, however it
introduced a bug how the upper part was encoded:
SPTE bits 52-61 were supposed to contain bits 10-19 of the current
generation number, however a missing shift encoded bits 1-10 there instead
(mostly duplicating the lower part of the encoded generation number that
then consisted of bits 1-9).
In the meantime, the upper part was shrunk by one bit and moved by
subsequent commits to become an upper half of the encoded generation number
(bits 9-17 of bits 0-17 encoded in a SPTE).
In addition to the above, commit 56871d444bc4 ("KVM: x86: fix overlap between SPTE_MMIO_MASK and generation")
has changed the SPTE bit range assigned to encode the generation number and
the total number of bits encoded but did not update them in the comment
attached to their defines, nor in the KVM MMU doc.
Let's do it here, too, since it is too trivial thing to warrant a separate
commit.
Fixes: cae7ed3c2cb0 ("KVM: x86: Refactor the MMIO SPTE generation handling")
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
---
Good catch. What do you think about this alternative definition? It
computes everything from the bit ranges.
#define MMIO_SPTE_GEN_LOW_START 3
#define MMIO_SPTE_GEN_LOW_END 11
#define MMIO_SPTE_GEN_HIGH_START PT64_SECOND_AVAIL_BITS_SHIFT
#define MMIO_SPTE_GEN_HIGH_END 62
#define MMIO_SPTE_GEN_LOW_MASK GENMASK_ULL(MMIO_SPTE_GEN_LOW_END, \
MMIO_SPTE_GEN_LOW_START)
#define MMIO_SPTE_GEN_HIGH_MASK
GENMASK_ULL(MMIO_SPTE_GEN_HIGH_END, \
MMIO_SPTE_GEN_HIGH_START)
#define MMIO_SPTE_GEN_LOW_BITS (MMIO_SPTE_GEN_LOW_END -
MMIO_SPTE_GEN_LOW_START + 1)
#define MMIO_SPTE_GEN_HIGH_BITS (MMIO_SPTE_GEN_HIGH_END -
MMIO_SPTE_GEN_HIGH_START + 1)
#define MMIO_SPTE_GEN_LOW_SHIFT (MMIO_SPTE_GEN_LOW_START - 0)
#define MMIO_SPTE_GEN_HIGH_SHIFT (MMIO_SPTE_GEN_HIGH_START -
MMIO_SPTE_GEN_LOW_BITS)
#define MMIO_SPTE_GEN_MASK
GENMASK_ULL(MMIO_SPTE_GEN_LOW_BITS + MMIO_SPTE_GEN_HIGH_BITS - 1, 0)
Thanks,
Paolo
