From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-devel@nongnu.org
Cc: Alex Williamson <alex.williamson@redhat.com>,
qemu-ppc@nongnu.org, David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH qemu] vfio/spapr: Fix page size calculation
Date: Tue, 24 Mar 2020 14:27:35 +0100 [thread overview]
Message-ID: <87ddd733-8498-57a5-2fe2-8f1a3e60e0c9@redhat.com> (raw)
In-Reply-To: <20200324063912.25063-1-aik@ozlabs.ru>
On 3/24/20 7:39 AM, Alexey Kardashevskiy wrote:
> Coverity detected an issue (CID 1421903) with potential call of clz64(0)
> which returns 64 which make it do "<<" with a negative number.
>
> This checks the mask and avoids undefined behaviour.
>
> In practice pgsizes and memory_region_iommu_get_min_page_size() always
> have some common page sizes and even if they did not, the resulting page
> size would be 0x8000.0000.0000.0000 (gcc 9.2) and
> ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> hw/vfio/spapr.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index 33692fc86fd6..2900bd19417a 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
> {
> int ret = 0;
> IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
> - uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
> + uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
> unsigned entries, bits_total, bits_per_level, max_levels;
> struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> long rampagesize = qemu_minrampagesize();
> @@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
> if (pagesize > rampagesize) {
> pagesize = rampagesize;
> }
> - pagesize = 1ULL << (63 - clz64(container->pgsizes &
> - (pagesize | (pagesize - 1))));
> + pgmask = container->pgsizes & (pagesize | (pagesize - 1));
Is that ROUND_UP(container->pgsizes, pagesize)?
> + pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
> if (!pagesize) {
> error_report("Host doesn't support page size 0x%"PRIx64
> ", the supported mask is 0x%lx",
>
next prev parent reply other threads:[~2020-03-24 13:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 6:39 [PATCH qemu] vfio/spapr: Fix page size calculation Alexey Kardashevskiy
2020-03-24 13:27 ` Philippe Mathieu-Daudé [this message]
2020-03-24 14:30 ` Greg Kurz
2020-03-24 14:47 ` Philippe Mathieu-Daudé
2020-03-24 14:29 ` Greg Kurz
2020-03-26 0:11 ` David Gibson
2020-03-26 11:21 ` Peter Maydell
2020-03-26 11:28 ` David Gibson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87ddd733-8498-57a5-2fe2-8f1a3e60e0c9@redhat.com \
--to=philmd@redhat.com \
--cc=aik@ozlabs.ru \
--cc=alex.williamson@redhat.com \
--cc=david@gibson.dropbear.id.au \
--cc=qemu-devel@nongnu.org \
--cc=qemu-ppc@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).