* [PATCH 0/3] GICv3: Bounds check redistributor accesses
@ 2017-10-11 9:41 Punit Agrawal
2017-10-11 9:41 ` [PATCH 1/3] irqchip/gic-v3: Use resource structure to store redistributor regions Punit Agrawal
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Punit Agrawal @ 2017-10-11 9:41 UTC (permalink / raw)
To: linux-arm-kernel
Hi,
While bringing up linux on a platform with GICv3, I ran into a kernel
crash (data abort) due to incorrectly sized GIC redistributor region
in the device tree.
Even though the firmware is expected to provide incorrect information,
crashing on the kernel's part when that is not the case is also not
ideal.
This series adds bounds checking to redistributor accesses. This
prevents the crash. But we can do one better - when the redistributor
region has been exhausted without encountering the last record the
user is warned of this situation. This can be useful for developers
during board bring-up.
Patch 3 is where the bulk of the checking is introduced. The patch is
a bit invasive but there doesn't seem to be a nicer way to isolate the
change given layout of the redistributor.
Feedback welcome.
Thanks,
Punit
Punit Agrawal (3):
irqchip/gic-v3: Use resource structure to store redistributor regions
irqchip/gic-v3: Report firmwware provided address in case of error
irqchip/gic-v3: Bounds check redistributor accesses
drivers/irqchip/irq-gic-v3.c | 80 +++++++++++++++++++++++++++++++++-----------
1 file changed, 61 insertions(+), 19 deletions(-)
--
2.14.1
^ permalink raw reply [flat|nested] 8+ messages in thread* [PATCH 1/3] irqchip/gic-v3: Use resource structure to store redistributor regions 2017-10-11 9:41 [PATCH 0/3] GICv3: Bounds check redistributor accesses Punit Agrawal @ 2017-10-11 9:41 ` Punit Agrawal 2017-10-11 9:41 ` [PATCH 2/3] irqchip/gic-v3: Report firmwware provided address in case of error Punit Agrawal 2017-10-11 9:41 ` [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses Punit Agrawal 2 siblings, 0 replies; 8+ messages in thread From: Punit Agrawal @ 2017-10-11 9:41 UTC (permalink / raw) To: linux-arm-kernel We don't store the size of the redistributor region required to prevent out of bounds accesses to incorrectly sized regions provided by the firmware. Instead of only storing the base address, store the redistributor region as a resource structure. The resource structure will be used in subsequent commits to add bounds checking to redistributor region accesses. Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> --- drivers/irqchip/irq-gic-v3.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index b5df99c6f680..8cb383b6e605 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -43,7 +43,7 @@ struct redist_region { void __iomem *redist_base; - phys_addr_t phys_base; + struct resource res; bool single_redist; }; @@ -481,7 +481,7 @@ static int __gic_populate_rdist(struct redist_region *region, void __iomem *ptr) if ((typer >> 32) == aff) { u64 offset = ptr - region->redist_base; gic_data_rdist_rd_base() = ptr; - gic_data_rdist()->phys_base = region->phys_base + offset; + gic_data_rdist()->phys_base = region->res.start + offset; pr_info("CPU%d: found redistributor %lx region %d:%pa\n", smp_processor_id(), mpidr, @@ -1206,17 +1206,18 @@ static int __init gic_of_init(struct device_node *node, struct device_node *pare } for (i = 0; i < nr_redist_regions; i++) { - struct resource res; + struct resource *res; int ret; - ret = of_address_to_resource(node, 1 + i, &res); - rdist_regs[i].redist_base = of_iomap(node, 1 + i); + res = &rdist_regs[i].res; + + ret = of_address_to_resource(node, 1 + i, res); + rdist_regs[i].redist_base = ioremap(res->start, resource_size(res)); if (ret || !rdist_regs[i].redist_base) { pr_err("%pOF: couldn't map region %d\n", node, i); err = -ENODEV; goto out_unmap_rdist; } - rdist_regs[i].phys_base = res.start; } if (of_property_read_u64(node, "redistributor-stride", &redist_stride)) @@ -1256,11 +1257,11 @@ static struct } acpi_data __initdata; static void __init -gic_acpi_register_redist(phys_addr_t phys_base, void __iomem *redist_base) +gic_acpi_register_redist(struct resource *res, void __iomem *redist_base) { static int count = 0; - acpi_data.redist_regs[count].phys_base = phys_base; + acpi_data.redist_regs[count].res = *res; acpi_data.redist_regs[count].redist_base = redist_base; acpi_data.redist_regs[count].single_redist = acpi_data.single_redist; count++; @@ -1273,6 +1274,10 @@ gic_acpi_parse_madt_redist(struct acpi_subtable_header *header, struct acpi_madt_generic_redistributor *redist = (struct acpi_madt_generic_redistributor *)header; void __iomem *redist_base; + struct resource redist_res; + + redist_res.start = redist->base_address; + redist_res.end = redist_res.start + redist->length - 1; redist_base = ioremap(redist->base_address, redist->length); if (!redist_base) { @@ -1280,7 +1285,7 @@ gic_acpi_parse_madt_redist(struct acpi_subtable_header *header, return -ENOMEM; } - gic_acpi_register_redist(redist->base_address, redist_base); + gic_acpi_register_redist(&redist_res, redist_base); return 0; } @@ -1293,12 +1298,16 @@ gic_acpi_parse_madt_gicc(struct acpi_subtable_header *header, u32 reg = readl_relaxed(acpi_data.dist_base + GICD_PIDR2) & GIC_PIDR2_ARCH_MASK; u32 size = reg == GIC_PIDR2_ARCH_GICv4 ? SZ_64K * 4 : SZ_64K * 2; void __iomem *redist_base; + struct resource res; redist_base = ioremap(gicc->gicr_base_address, size); if (!redist_base) return -ENOMEM; - gic_acpi_register_redist(gicc->gicr_base_address, redist_base); + res.start = gicc->gicr_base_address; + res.end = res.start + size - 1; + + gic_acpi_register_redist(&res, redist_base); return 0; } -- 2.14.1 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 2/3] irqchip/gic-v3: Report firmwware provided address in case of error 2017-10-11 9:41 [PATCH 0/3] GICv3: Bounds check redistributor accesses Punit Agrawal 2017-10-11 9:41 ` [PATCH 1/3] irqchip/gic-v3: Use resource structure to store redistributor regions Punit Agrawal @ 2017-10-11 9:41 ` Punit Agrawal 2017-10-11 9:41 ` [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses Punit Agrawal 2 siblings, 0 replies; 8+ messages in thread From: Punit Agrawal @ 2017-10-11 9:41 UTC (permalink / raw) To: linux-arm-kernel When a redistributor is not found at the address provided by the firmware, report the firmware provided address to help user identify the offending firmware data. Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> --- drivers/irqchip/irq-gic-v3.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index 8cb383b6e605..881d327c53fa 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -430,13 +430,14 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) for (i = 0; i < gic_data.nr_redist_regions; i++) { void __iomem *ptr = gic_data.redist_regions[i].redist_base; + struct resource *res = &gic_data.redist_regions[i].res; u64 typer; u32 reg; reg = readl_relaxed(ptr + GICR_PIDR2) & GIC_PIDR2_ARCH_MASK; if (reg != GIC_PIDR2_ARCH_GICv3 && reg != GIC_PIDR2_ARCH_GICv4) { /* We're in trouble... */ - pr_warn("No redistributor present @%p\n", ptr); + pr_warn("No redistributor present @%llx\n", res->start); break; } -- 2.14.1 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses 2017-10-11 9:41 [PATCH 0/3] GICv3: Bounds check redistributor accesses Punit Agrawal 2017-10-11 9:41 ` [PATCH 1/3] irqchip/gic-v3: Use resource structure to store redistributor regions Punit Agrawal 2017-10-11 9:41 ` [PATCH 2/3] irqchip/gic-v3: Report firmwware provided address in case of error Punit Agrawal @ 2017-10-11 9:41 ` Punit Agrawal 2018-03-13 13:38 ` [3/3] " Lokesh Vutla 2 siblings, 1 reply; 8+ messages in thread From: Punit Agrawal @ 2017-10-11 9:41 UTC (permalink / raw) To: linux-arm-kernel The kernel crashes while iterating over a redistributor that is in-correctly sized by the platform firmware or doesn't contain the last record. Prevent the crash by checking accesses against the size of the region provided by the firmware. While we are at it, warn the user about incorrect region size. Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> --- drivers/irqchip/irq-gic-v3.c | 48 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 40 insertions(+), 8 deletions(-) diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index 881d327c53fa..754d936c95e5 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -429,11 +429,21 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) int i; for (i = 0; i < gic_data.nr_redist_regions; i++) { - void __iomem *ptr = gic_data.redist_regions[i].redist_base; struct resource *res = &gic_data.redist_regions[i].res; - u64 typer; + void __iomem *ptr, *base; + u64 typer, size, stride; u32 reg; + ptr = base = gic_data.redist_regions[i].redist_base; + size = resource_size(res); + + stride = gic_data.redist_stride ?: SZ_64K * 2; + if (ptr + stride > base + size) { + pr_warn("Insufficient size for redistributor region @%llx. Skipping\n", + res->start); + continue; + } + reg = readl_relaxed(ptr + GICR_PIDR2) & GIC_PIDR2_ARCH_MASK; if (reg != GIC_PIDR2_ARCH_GICv3 && reg != GIC_PIDR2_ARCH_GICv4) { /* We're in trouble... */ @@ -442,7 +452,28 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) } do { + /* + * We can access GICR_TYPER as we have already + * checked that we have atleast 128kB or + * redist_stride + */ typer = gic_read_typer(ptr + GICR_TYPER); + if (!gic_data.redist_stride && + (typer & GICR_TYPER_VLPIS)) { + /* VLPI_base + reserved page */ + stride += SZ_64K * 2; + + /* + * We are larger than we thought, do + * we still fit? + */ + if (ptr + stride > base + size) { + pr_warn("No last record found in redistributor region @%llx\n", + gic_data.redist_regions[i].res.start); + break; + } + } + ret = fn(gic_data.redist_regions + i, ptr); if (!ret) return 0; @@ -450,12 +481,13 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) if (gic_data.redist_regions[i].single_redist) break; - if (gic_data.redist_stride) { - ptr += gic_data.redist_stride; - } else { - ptr += SZ_64K * 2; /* Skip RD_base + SGI_base */ - if (typer & GICR_TYPER_VLPIS) - ptr += SZ_64K * 2; /* Skip VLPI_base + reserved page */ + ptr += stride; + + stride = gic_data.redist_stride ?: SZ_64K * 2; + if (ptr + stride > base + size) { + pr_warn("No last record found in redistributor region @%llx\n", + gic_data.redist_regions[i].res.start); + break; } } while (!(typer & GICR_TYPER_LAST)); } -- 2.14.1 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* [3/3] irqchip/gic-v3: Bounds check redistributor accesses 2017-10-11 9:41 ` [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses Punit Agrawal @ 2018-03-13 13:38 ` Lokesh Vutla 2018-03-13 14:21 ` Marc Zyngier 0 siblings, 1 reply; 8+ messages in thread From: Lokesh Vutla @ 2018-03-13 13:38 UTC (permalink / raw) To: linux-arm-kernel Hi All, On Wednesday 11 October 2017 03:11 PM, Punit Agrawal wrote: > The kernel crashes while iterating over a redistributor that is > in-correctly sized by the platform firmware or doesn't contain the last > record. > > Prevent the crash by checking accesses against the size of the region > provided by the firmware. While we are at it, warn the user about > incorrect region size. > > Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> > Cc: Marc Zyngier <marc.zyngier@arm.com> Sorry to bring up an old thread. Just wanted to check what is the status on this series. This will also be useful when we try to boot linux + hypervisor with less number of cores than the SoC supports. For example: - SoC has 4 cores and Linux tries to boot with 2 cores. - then a type-2 hypervisor gets installed. - Hypervisor tries to boot a VM with linux on core 1. Now the VM boot will fail while it iterates over all the GICR regions till GICR_TYPER is found. Hypervisor will trap any accesses to GICR regions of any invalid cpus(cpu 2, cpu 3 in this case). If the $patch is not the right approach, can you suggest on how to handle the above scenario? Thanks and regards, Lokesh > --- > drivers/irqchip/irq-gic-v3.c | 48 ++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 40 insertions(+), 8 deletions(-) > > diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c > index 881d327c53fa..754d936c95e5 100644 > --- a/drivers/irqchip/irq-gic-v3.c > +++ b/drivers/irqchip/irq-gic-v3.c > @@ -429,11 +429,21 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) > int i; > > for (i = 0; i < gic_data.nr_redist_regions; i++) { > - void __iomem *ptr = gic_data.redist_regions[i].redist_base; > struct resource *res = &gic_data.redist_regions[i].res; > - u64 typer; > + void __iomem *ptr, *base; > + u64 typer, size, stride; > u32 reg; > > + ptr = base = gic_data.redist_regions[i].redist_base; > + size = resource_size(res); > + > + stride = gic_data.redist_stride ?: SZ_64K * 2; > + if (ptr + stride > base + size) { > + pr_warn("Insufficient size for redistributor region @%llx. Skipping\n", > + res->start); > + continue; > + } > + > reg = readl_relaxed(ptr + GICR_PIDR2) & GIC_PIDR2_ARCH_MASK; > if (reg != GIC_PIDR2_ARCH_GICv3 && > reg != GIC_PIDR2_ARCH_GICv4) { /* We're in trouble... */ > @@ -442,7 +452,28 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) > } > > do { > + /* > + * We can access GICR_TYPER as we have already > + * checked that we have atleast 128kB or > + * redist_stride > + */ > typer = gic_read_typer(ptr + GICR_TYPER); > + if (!gic_data.redist_stride && > + (typer & GICR_TYPER_VLPIS)) { > + /* VLPI_base + reserved page */ > + stride += SZ_64K * 2; > + > + /* > + * We are larger than we thought, do > + * we still fit? > + */ > + if (ptr + stride > base + size) { > + pr_warn("No last record found in redistributor region @%llx\n", > + gic_data.redist_regions[i].res.start); > + break; > + } > + } > + > ret = fn(gic_data.redist_regions + i, ptr); > if (!ret) > return 0; > @@ -450,12 +481,13 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *)) > if (gic_data.redist_regions[i].single_redist) > break; > > - if (gic_data.redist_stride) { > - ptr += gic_data.redist_stride; > - } else { > - ptr += SZ_64K * 2; /* Skip RD_base + SGI_base */ > - if (typer & GICR_TYPER_VLPIS) > - ptr += SZ_64K * 2; /* Skip VLPI_base + reserved page */ > + ptr += stride; > + > + stride = gic_data.redist_stride ?: SZ_64K * 2; > + if (ptr + stride > base + size) { > + pr_warn("No last record found in redistributor region @%llx\n", > + gic_data.redist_regions[i].res.start); > + break; > } > } while (!(typer & GICR_TYPER_LAST)); > } > ^ permalink raw reply [flat|nested] 8+ messages in thread
* [3/3] irqchip/gic-v3: Bounds check redistributor accesses 2018-03-13 13:38 ` [3/3] " Lokesh Vutla @ 2018-03-13 14:21 ` Marc Zyngier 2018-03-13 18:49 ` Nishanth Menon 0 siblings, 1 reply; 8+ messages in thread From: Marc Zyngier @ 2018-03-13 14:21 UTC (permalink / raw) To: linux-arm-kernel Hi Lokesh, On 13/03/18 13:38, Lokesh Vutla wrote: > Hi All, > > On Wednesday 11 October 2017 03:11 PM, Punit Agrawal wrote: >> The kernel crashes while iterating over a redistributor that is >> in-correctly sized by the platform firmware or doesn't contain the last >> record. >> >> Prevent the crash by checking accesses against the size of the region >> provided by the firmware. While we are at it, warn the user about >> incorrect region size. >> >> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> >> Cc: Marc Zyngier <marc.zyngier@arm.com> > > Sorry to bring up an old thread. Just wanted to check what is the status > on this series. So far, I wasn't inclined to merge it, as it only allowed you to detect a broken system, as opposed to help with a working one. > This will also be useful when we try to boot linux + hypervisor with > less number of cores than the SoC supports. For example: > - SoC has 4 cores and Linux tries to boot with 2 cores. > - then a type-2 hypervisor gets installed. > - Hypervisor tries to boot a VM with linux on core 1. > > Now the VM boot will fail while it iterates over all the GICR regions > till GICR_TYPER is found. Hypervisor will trap any accesses to GICR > regions of any invalid cpus(cpu 2, cpu 3 in this case). It you're passing the redistributors to a guest, you're doing something terribly wrong. You're putting the guest in a position to do a DoS on the hypervisor (disabling its timer interrupt, for example). Not the greatest move. There is a number of other gotchas with this approach (virtual interrupts, distributor virtualization...). > If the $patch is not the right approach, can you suggest on how to > handle the above scenario? The proper way to handle this is to virtualize the distributor and redistributor by trap/emulate. The only thing you can safely pass to a guest is the CPU interface, either as system registers or in its MMIO form (if you have the GICv2 compatibility interface). Thanks, M. -- Jazz is not dead. It just smells funny... ^ permalink raw reply [flat|nested] 8+ messages in thread
* [3/3] irqchip/gic-v3: Bounds check redistributor accesses 2018-03-13 14:21 ` Marc Zyngier @ 2018-03-13 18:49 ` Nishanth Menon 2018-03-13 20:19 ` Marc Zyngier 0 siblings, 1 reply; 8+ messages in thread From: Nishanth Menon @ 2018-03-13 18:49 UTC (permalink / raw) To: linux-arm-kernel Marc, On Tue, Mar 13, 2018 at 9:21 AM, Marc Zyngier <marc.zyngier@arm.com> wrote: > Hi Lokesh, > > On 13/03/18 13:38, Lokesh Vutla wrote: >> Hi All, >> >> On Wednesday 11 October 2017 03:11 PM, Punit Agrawal wrote: >>> The kernel crashes while iterating over a redistributor that is >>> in-correctly sized by the platform firmware or doesn't contain the last >>> record. >>> >>> Prevent the crash by checking accesses against the size of the region >>> provided by the firmware. While we are at it, warn the user about >>> incorrect region size. >>> >>> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> >>> Cc: Marc Zyngier <marc.zyngier@arm.com> >> >> Sorry to bring up an old thread. Just wanted to check what is the status >> on this series. > > So far, I wasn't inclined to merge it, as it only allowed you to detect > a broken system, as opposed to help with a working one. Is'nt that a good reason to have it? Why not help an error in dtb with a debug helper than an obtuse crash to debug painfully? > >> This will also be useful when we try to boot linux + hypervisor with >> less number of cores than the SoC supports. For example: >> - SoC has 4 cores and Linux tries to boot with 2 cores. >> - then a type-2 hypervisor gets installed. >> - Hypervisor tries to boot a VM with linux on core 1. >> >> Now the VM boot will fail while it iterates over all the GICR regions >> till GICR_TYPER is found. Hypervisor will trap any accesses to GICR >> regions of any invalid cpus(cpu 2, cpu 3 in this case). > > It you're passing the redistributors to a guest, you're doing something > terribly wrong. You're putting the guest in a position to do a DoS on > the hypervisor (disabling its timer interrupt, for example). Not the > greatest move. There is a number of other gotchas with this approach > (virtual interrupts, distributor virtualization...). > >> If the $patch is not the right approach, can you suggest on how to >> handle the above scenario? > > The proper way to handle this is to virtualize the distributor and > redistributor by trap/emulate. The only thing you can safely pass to a > guest is the CPU interface, either as system registers or in its MMIO > form (if you have the GICv2 compatibility interface). > Dumb question: Would'nt a trap emulate be real expensive with hyp context in v8 (all the context save/restore we'd have to do? (in the context of discussion, GICV2 compat is disabled). -- --- Regards, Nishanth Menon ^ permalink raw reply [flat|nested] 8+ messages in thread
* [3/3] irqchip/gic-v3: Bounds check redistributor accesses 2018-03-13 18:49 ` Nishanth Menon @ 2018-03-13 20:19 ` Marc Zyngier 0 siblings, 0 replies; 8+ messages in thread From: Marc Zyngier @ 2018-03-13 20:19 UTC (permalink / raw) To: linux-arm-kernel On Tue, 13 Mar 2018 18:49:44 +0000, Nishanth Menon wrote: > > Marc, > > On Tue, Mar 13, 2018 at 9:21 AM, Marc Zyngier <marc.zyngier@arm.com> wrote: > > Hi Lokesh, > > > > On 13/03/18 13:38, Lokesh Vutla wrote: > >> Hi All, > >> > >> On Wednesday 11 October 2017 03:11 PM, Punit Agrawal wrote: > >>> The kernel crashes while iterating over a redistributor that is > >>> in-correctly sized by the platform firmware or doesn't contain the last > >>> record. > >>> > >>> Prevent the crash by checking accesses against the size of the region > >>> provided by the firmware. While we are at it, warn the user about > >>> incorrect region size. > >>> > >>> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> > >>> Cc: Marc Zyngier <marc.zyngier@arm.com> > >> > >> Sorry to bring up an old thread. Just wanted to check what is the status > >> on this series. > > > > So far, I wasn't inclined to merge it, as it only allowed you to detect > > a broken system, as opposed to help with a working one. > > Is'nt that a good reason to have it? Why not help an error in dtb with > a debug helper than an obtuse crash to debug painfully? The kernel is not in the business of validating DTBs. And we both know that if we start papering over firmware bugs, these bugs become ABI, and we live with them forever. If you want to validate DTBs, you should use a tool that is actually validating it against your HW, and not use the kernel as the validation tool. > > > > >> This will also be useful when we try to boot linux + hypervisor with > >> less number of cores than the SoC supports. For example: > >> - SoC has 4 cores and Linux tries to boot with 2 cores. > >> - then a type-2 hypervisor gets installed. > >> - Hypervisor tries to boot a VM with linux on core 1. > >> > >> Now the VM boot will fail while it iterates over all the GICR regions > >> till GICR_TYPER is found. Hypervisor will trap any accesses to GICR > >> regions of any invalid cpus(cpu 2, cpu 3 in this case). > > > > It you're passing the redistributors to a guest, you're doing something > > terribly wrong. You're putting the guest in a position to do a DoS on > > the hypervisor (disabling its timer interrupt, for example). Not the > > greatest move. There is a number of other gotchas with this approach > > (virtual interrupts, distributor virtualization...). > > > >> If the $patch is not the right approach, can you suggest on how to > >> handle the above scenario? > > > > The proper way to handle this is to virtualize the distributor and > > redistributor by trap/emulate. The only thing you can safely pass to a > > guest is the CPU interface, either as system registers or in its MMIO > > form (if you have the GICv2 compatibility interface). > > > > Dumb question: Would'nt a trap emulate be real expensive with hyp > context in v8 (all the context save/restore we'd have to do? (in the > context of discussion, GICV2 compat is disabled). How often do you hit the distributor and redistributors? Why do you need to context switch a distributor that you emulate (hint: you don't). I suggest you look at how real life hypervisor works (there's a pretty good one in the tree). Thanks, M. -- Jazz is not dead, it just smell funny. ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2018-03-13 20:19 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2017-10-11 9:41 [PATCH 0/3] GICv3: Bounds check redistributor accesses Punit Agrawal 2017-10-11 9:41 ` [PATCH 1/3] irqchip/gic-v3: Use resource structure to store redistributor regions Punit Agrawal 2017-10-11 9:41 ` [PATCH 2/3] irqchip/gic-v3: Report firmwware provided address in case of error Punit Agrawal 2017-10-11 9:41 ` [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses Punit Agrawal 2018-03-13 13:38 ` [3/3] " Lokesh Vutla 2018-03-13 14:21 ` Marc Zyngier 2018-03-13 18:49 ` Nishanth Menon 2018-03-13 20:19 ` Marc Zyngier
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