> -----Original Message-----
> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of Roger
> Pau Monne
> Sent: 30 September 2019 14:32
> To: xen-devel@lists.xenproject.org
> Cc: Andrew Cooper <andrew.coop...@citrix.com>; Paul Durrant <p...@xen.org>;
> Wei Liu <w...@xen.org>; Jan
> Beulich <jbeul...@suse.com>; Roger Pau Monne <roger....@citrix.com>
> Subject: [Xen-devel] [PATCH v3 01/10] ioreq: terminate cf8 handling at
> hypervisor level
>
> Do not forward accesses to cf8 to external emulators, decoding of PCI
> accesses is handled by Xen, and emulators can request handling of
> config space accesses of devices using the provided ioreq interface.
>
> Fully terminate cf8 accesses at the hypervisor level, by improving the
> existing hvm_access_cf8 helper to also handle register reads, and
> always return X86EMUL_OKAY in order to terminate the emulation.
>
> Note that without this change in the absence of some external emulator
> that catches accesses to cf8 read requests to the register would
> misbehave, as the ioreq internal handler did not handle those.
>
> Signed-off-by: Roger Pau Monné <roger....@citrix.com>
Reviewed-by: Paul Durrant <p...@xen.org>
> ---
> Changes since v2:
> - Allow ioreq servers to map 0xcf8 and 0xcfc, even if those are
> handled by the hypervisor.
>
> Changes since v1:
> - New in this version.
> ---
> xen/arch/x86/hvm/ioreq.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
> index d347144096..5e503ce498 100644
> --- a/xen/arch/x86/hvm/ioreq.c
> +++ b/xen/arch/x86/hvm/ioreq.c
> @@ -1518,11 +1518,15 @@ static int hvm_access_cf8(
> {
> struct domain *d = current->domain;
>
> - if ( dir == IOREQ_WRITE && bytes == 4 )
> + if ( bytes != 4 )
> + return X86EMUL_OKAY;
> +
> + if ( dir == IOREQ_WRITE )
> d->arch.hvm.pci_cf8 = *val;
> + else
> + *val = d->arch.hvm.pci_cf8;
>
> - /* We always need to fall through to the catch all emulator */
> - return X86EMUL_UNHANDLEABLE;
> + return X86EMUL_OKAY;
> }
>
> void hvm_ioreq_init(struct domain *d)
> --
> 2.23.0
>
>
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