> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 18 May 2018 14:34 > To: Paul Durrant <paul.durr...@citrix.com> > Cc: Anthony Perard <anthony.per...@citrix.com>; Roger Pau Monne > <roger....@citrix.com>; Stefano Stabellini <sstabell...@kernel.org>; xen- > devel <xen-de...@lists.xenproject.org>; qemu-devel@nongnu.org; > ehabk...@redhat.com; mar...@redhat.com; m...@redhat.com; Paolo > Bonzini <pbonz...@redhat.com>; Richard Henderson <r...@twiddle.net> > Subject: Re: [Xen-devel] [PATCH v2] xen-hvm: stop faking I/O to access PCI > config space > > >>> On 18.05.18 at 15:00, <paul.durr...@citrix.com> wrote: > > @@ -903,6 +926,80 @@ static void cpu_ioreq_move(ioreq_t *req) > > } > > } > > > > +static void rw_config_req_item(XenPciDevice *xendev, ioreq_t *req, > > It looks to me as if both parameters could be constified. >
They could for this function, yes. > > + uint32_t i, uint32_t *val) > > +{ > > + int32_t reg = req->addr; > > + uint32_t offset = req->size * i; > > + > > + reg += (req->df ? -1 : 1) * offset; > > + if (reg < 0 || reg > PCI_CONFIG_SPACE_SIZE) { > > Having fought a number of issues in this area in the hypervisor a couple > of years back I wonder > - why reg is of signed type, I did that so I could do a < 0 check. > - whether overflow of the first multiplication really doesn't matter, It would be better to check it. > - whether wrapping when adding in the offset is not an issue. > I'll do limits check on offset then... should be able to make reg unsigned then I guess. > I take it that the rather lax upper bound check (should imo really be > reg + size > PCI_CONFIG_SPACE_SIZE [implying reg + size doesn't > itself wrap], or at least reg >= PCI_CONFIG_SPACE_SIZE) is not a > problem because ... > > > + if (req->dir == IOREQ_READ) { > > + *val = ~0u; > > + } > > + return; > > + } > > + > > + if (req->dir == IOREQ_READ) { > > + *val = pci_host_config_read_common(xendev->pci_dev, reg, > > + PCI_CONFIG_SPACE_SIZE, > > + req->size); > > + trace_cpu_ioreq_config_read(req, xendev->sbdf, reg, > > + req->size, *val); > > + } else { > > + trace_cpu_ioreq_config_write(req, xendev->sbdf, reg, req->size, > > + *val); > > + pci_host_config_write_common(xendev->pci_dev, reg, > > + PCI_CONFIG_SPACE_SIZE, *val, > > + req->size); > > + } > > ... these called functions do full checking anyway? Yes, I'm deferring further checking to these common functions. I'm only intending to avoid passing junk into them here. > > > +static void cpu_ioreq_config(XenIOState *state, ioreq_t *req) > > +{ > > + uint32_t sbdf = req->addr >> 32; > > + XenPciDevice *xendev; > > + > > + if (req->size > sizeof(uint32_t)) { > > + hw_error("PCI config access: bad size (%u)", req->size); > > What about size 0 or 3? > Yes, I can reject those here also. > > + } > > + > > + QLIST_FOREACH(xendev, &state->dev_list, entry) { > > + unsigned int i; > > + uint32_t tmp; > > + > > + if (xendev->sbdf != sbdf) { > > + continue; > > + } > > + > > + if (!req->data_is_ptr) { > > + if (req->dir == IOREQ_READ) { > > + for (i = 0; i < req->count; i++) { > > + rw_config_req_item(xendev, req, i, &tmp); > > + req->data = tmp; > > + } > > + } else if (req->dir == IOREQ_WRITE) { > > + for (i = 0; i < req->count; i++) { > > + tmp = req->data; > > + rw_config_req_item(xendev, req, i, &tmp); > > + } > > + } > > Wouldn't it be more sensible to fail req->count != 1 requests here? > I'm wondering whether we'd want to handle count > 1 once we allow MMCONFIG accesses though. I guess it would be easier just to defer that. Paul > Jan >