* dmapool regression in next
@ 2018-12-06 1:30 ` Tony Lindgren
0 siblings, 0 replies; 14+ messages in thread
From: Tony Lindgren @ 2018-12-06 1:30 UTC (permalink / raw)
To: Tony Battersby, Andrew Morton, Stephen Rothwell
Cc: Andy Shevchenko, Christoph Hellwig, John Garry, Marek Szyprowski,
Russell King - ARM Linux, linux-kernel, linux-arm-kernel,
linux-omap
Hi,
Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability
of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)"
on at least omap4 pandaboard, see below.
Any ideas what might be going wrong?
Regards,
Tony
8< ---------------------
omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000
omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c
omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038
...
^ permalink raw reply [flat|nested] 14+ messages in thread* dmapool regression in next @ 2018-12-06 1:30 ` Tony Lindgren 0 siblings, 0 replies; 14+ messages in thread From: Tony Lindgren @ 2018-12-06 1:30 UTC (permalink / raw) To: Tony Battersby, Andrew Morton, Stephen Rothwell Cc: John Garry, Russell King - ARM Linux, linux-kernel, Andy Shevchenko, linux-omap, Christoph Hellwig, linux-arm-kernel, Marek Szyprowski Hi, Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" on at least omap4 pandaboard, see below. Any ideas what might be going wrong? Regards, Tony 8< --------------------- omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 ... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next 2018-12-06 1:30 ` Tony Lindgren @ 2018-12-06 9:25 ` Krzysztof Kozlowski -1 siblings, 0 replies; 14+ messages in thread From: Krzysztof Kozlowski @ 2018-12-06 9:25 UTC (permalink / raw) To: tony Cc: tonyb, akpm, Stephen Rothwell, andy.shevchenko, hch, john.garry, Marek Szyprowski, linux, linux-kernel, linux-arm-kernel, linux-omap On Thu, 6 Dec 2018 at 02:31, Tony Lindgren <tony@atomide.com> wrote: > > Hi, > > Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability > of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" > on at least omap4 pandaboard, see below. > > Any ideas what might be going wrong? > > Regards, > > Tony > > 8< --------------------- > omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 > omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c > omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 > ... I see it as well on all my Exynos boards, since yesterday's next. In my case it is the USB EHCI driver: exynos-ehci 12110000.usb: dma_pool_free ehci_qtd, (ptrval) (bad vaddr)/0xb8844180 Full log here: https://krzk.eu/#/builders/1/builds/2937/steps/12/logs/serial0 Best regards, Krzysztof ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next @ 2018-12-06 9:25 ` Krzysztof Kozlowski 0 siblings, 0 replies; 14+ messages in thread From: Krzysztof Kozlowski @ 2018-12-06 9:25 UTC (permalink / raw) To: tony Cc: Stephen Rothwell, linux-kernel, john.garry, linux, hch, andy.shevchenko, akpm, linux-omap, tonyb, linux-arm-kernel, Marek Szyprowski On Thu, 6 Dec 2018 at 02:31, Tony Lindgren <tony@atomide.com> wrote: > > Hi, > > Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability > of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" > on at least omap4 pandaboard, see below. > > Any ideas what might be going wrong? > > Regards, > > Tony > > 8< --------------------- > omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 > omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c > omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 > ... I see it as well on all my Exynos boards, since yesterday's next. In my case it is the USB EHCI driver: exynos-ehci 12110000.usb: dma_pool_free ehci_qtd, (ptrval) (bad vaddr)/0xb8844180 Full log here: https://krzk.eu/#/builders/1/builds/2937/steps/12/logs/serial0 Best regards, Krzysztof _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next 2018-12-06 9:25 ` Krzysztof Kozlowski @ 2018-12-06 15:11 ` Tony Battersby -1 siblings, 0 replies; 14+ messages in thread From: Tony Battersby @ 2018-12-06 15:11 UTC (permalink / raw) To: Krzysztof Kozlowski, tony Cc: Stephen Rothwell, john.garry, linux, linux-kernel, andy.shevchenko, akpm, linux-omap, hch, linux-arm-kernel, Marek Szyprowski On 12/6/18 4:25 AM, Krzysztof Kozlowski wrote: > On Thu, 6 Dec 2018 at 02:31, Tony Lindgren <tony@atomide.com> wrote: >> Hi, >> >> Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability >> of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" >> on at least omap4 pandaboard, see below. >> >> Any ideas what might be going wrong? >> >> Regards, >> >> Tony >> >> 8< --------------------- >> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 >> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c >> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 >> ... > I see it as well on all my Exynos boards, since yesterday's next. In > my case it is the USB EHCI driver: > exynos-ehci 12110000.usb: dma_pool_free ehci_qtd, (ptrval) (bad > vaddr)/0xb8844180 > Full log here: > https://krzk.eu/#/builders/1/builds/2937/steps/12/logs/serial0 > > Best regards, > Krzysztof > Here is the prototype: void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); With the old code, the 'dma' value had to be correct for use with pool_find_page(), or else you would get an error. If the 'vaddr' value was incorrect, it would corrupt the dmapool freelist, but you wouldn't get an error unless DMAPOOL_DEBUG was enabled. With my patch applied, 'vaddr' has to be correct for virt_to_page(). My code also checks that 'dma' is consistent with 'vaddr' even if DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent problems like this in the future. So if a buggy driver passes in a good value for 'dma' but a bad value for 'vaddr', then it may have appeared to work previously (but with possible data corruption, depending on the circumstances), but my patch will expose the problem. You can confirm by reverting my dmapool patches and enabling DMAPOOL_DEBUG, which is at the top of mm/dmapool.c: #if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON) #define DMAPOOL_DEBUG 1 #endif Tony Battersby _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next @ 2018-12-06 15:11 ` Tony Battersby 0 siblings, 0 replies; 14+ messages in thread From: Tony Battersby @ 2018-12-06 15:11 UTC (permalink / raw) To: Krzysztof Kozlowski, tony Cc: akpm, Stephen Rothwell, andy.shevchenko, hch, john.garry, Marek Szyprowski, linux, linux-kernel, linux-arm-kernel, linux-omap On 12/6/18 4:25 AM, Krzysztof Kozlowski wrote: > On Thu, 6 Dec 2018 at 02:31, Tony Lindgren <tony@atomide.com> wrote: >> Hi, >> >> Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability >> of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" >> on at least omap4 pandaboard, see below. >> >> Any ideas what might be going wrong? >> >> Regards, >> >> Tony >> >> 8< --------------------- >> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 >> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c >> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 >> ... > I see it as well on all my Exynos boards, since yesterday's next. In > my case it is the USB EHCI driver: > exynos-ehci 12110000.usb: dma_pool_free ehci_qtd, (ptrval) (bad > vaddr)/0xb8844180 > Full log here: > https://krzk.eu/#/builders/1/builds/2937/steps/12/logs/serial0 > > Best regards, > Krzysztof > Here is the prototype: void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); With the old code, the 'dma' value had to be correct for use with pool_find_page(), or else you would get an error. If the 'vaddr' value was incorrect, it would corrupt the dmapool freelist, but you wouldn't get an error unless DMAPOOL_DEBUG was enabled. With my patch applied, 'vaddr' has to be correct for virt_to_page(). My code also checks that 'dma' is consistent with 'vaddr' even if DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent problems like this in the future. So if a buggy driver passes in a good value for 'dma' but a bad value for 'vaddr', then it may have appeared to work previously (but with possible data corruption, depending on the circumstances), but my patch will expose the problem. You can confirm by reverting my dmapool patches and enabling DMAPOOL_DEBUG, which is at the top of mm/dmapool.c: #if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON) #define DMAPOOL_DEBUG 1 #endif Tony Battersby ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next 2018-12-06 15:11 ` Tony Battersby @ 2018-12-06 15:51 ` Robin Murphy -1 siblings, 0 replies; 14+ messages in thread From: Robin Murphy @ 2018-12-06 15:51 UTC (permalink / raw) To: Tony Battersby, Krzysztof Kozlowski, tony Cc: Stephen Rothwell, john.garry, linux, linux-kernel, andy.shevchenko, akpm, linux-omap, hch, linux-arm-kernel, Marek Szyprowski On 06/12/2018 15:11, Tony Battersby wrote: > On 12/6/18 4:25 AM, Krzysztof Kozlowski wrote: >> On Thu, 6 Dec 2018 at 02:31, Tony Lindgren <tony@atomide.com> wrote: >>> Hi, >>> >>> Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability >>> of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" >>> on at least omap4 pandaboard, see below. >>> >>> Any ideas what might be going wrong? >>> >>> Regards, >>> >>> Tony >>> >>> 8< --------------------- >>> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 >>> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c >>> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 >>> ... >> I see it as well on all my Exynos boards, since yesterday's next. In >> my case it is the USB EHCI driver: >> exynos-ehci 12110000.usb: dma_pool_free ehci_qtd, (ptrval) (bad >> vaddr)/0xb8844180 >> Full log here: >> https://krzk.eu/#/builders/1/builds/2937/steps/12/logs/serial0 >> >> Best regards, >> Krzysztof >> > Here is the prototype: > > void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); > > With the old code, the 'dma' value had to be correct for use with > pool_find_page(), or else you would get an error. If the 'vaddr' value > was incorrect, it would corrupt the dmapool freelist, but you wouldn't > get an error unless DMAPOOL_DEBUG was enabled. > > With my patch applied, 'vaddr' has to be correct for virt_to_page(). My > code also checks that 'dma' is consistent with 'vaddr' even if > DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent > problems like this in the future. Unfortunately that logic has a fatal flaw - DMA pools are backed by dma_alloc_coherent(), and there is absolutely no guarantee that the memory dma_alloc_coherent() returns is backed by a struct page at all. Even if it is, there is still absolutely no guarantee that the vaddr value it returns is valid for virt_to_page() - on many systems it will be in vmalloc or some architecture-specific region of address space. The problem is not that these drivers are buggy (they're not - the arch code is returning a vmalloc()ed non-cacheable remap in the first place), it's that 26abe88e830d is fundamentally unworkable and needs reverting. Apparently the original patches managed not to catch my eye as something I needed to review, sorry about that :( Robin. > > So if a buggy driver passes in a good value for 'dma' but a bad value > for 'vaddr', then it may have appeared to work previously (but with > possible data corruption, depending on the circumstances), but my patch > will expose the problem. You can confirm by reverting my dmapool > patches and enabling DMAPOOL_DEBUG, which is at the top of mm/dmapool.c: > > #if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON) > #define DMAPOOL_DEBUG 1 > #endif > > Tony Battersby > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next @ 2018-12-06 15:51 ` Robin Murphy 0 siblings, 0 replies; 14+ messages in thread From: Robin Murphy @ 2018-12-06 15:51 UTC (permalink / raw) To: Tony Battersby, Krzysztof Kozlowski, tony Cc: Stephen Rothwell, john.garry, linux, linux-kernel, andy.shevchenko, akpm, linux-omap, hch, linux-arm-kernel, Marek Szyprowski On 06/12/2018 15:11, Tony Battersby wrote: > On 12/6/18 4:25 AM, Krzysztof Kozlowski wrote: >> On Thu, 6 Dec 2018 at 02:31, Tony Lindgren <tony@atomide.com> wrote: >>> Hi, >>> >>> Looks like with commit 26abe88e830d ("mm/dmapool.c: improve scalability >>> of dma_pool_free()") I'm now getting spammed with lots of "(bad vaddr)" >>> on at least omap4 pandaboard, see below. >>> >>> Any ideas what might be going wrong? >>> >>> Regards, >>> >>> Tony >>> >>> 8< --------------------- >>> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800000 >>> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe80001c >>> omap-dma-engine 4a056000.dma-controller: dma_pool_free 4a056000.dma-controller, (ptrval) (bad vaddr)/0xbe800038 >>> ... >> I see it as well on all my Exynos boards, since yesterday's next. In >> my case it is the USB EHCI driver: >> exynos-ehci 12110000.usb: dma_pool_free ehci_qtd, (ptrval) (bad >> vaddr)/0xb8844180 >> Full log here: >> https://krzk.eu/#/builders/1/builds/2937/steps/12/logs/serial0 >> >> Best regards, >> Krzysztof >> > Here is the prototype: > > void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); > > With the old code, the 'dma' value had to be correct for use with > pool_find_page(), or else you would get an error. If the 'vaddr' value > was incorrect, it would corrupt the dmapool freelist, but you wouldn't > get an error unless DMAPOOL_DEBUG was enabled. > > With my patch applied, 'vaddr' has to be correct for virt_to_page(). My > code also checks that 'dma' is consistent with 'vaddr' even if > DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent > problems like this in the future. Unfortunately that logic has a fatal flaw - DMA pools are backed by dma_alloc_coherent(), and there is absolutely no guarantee that the memory dma_alloc_coherent() returns is backed by a struct page at all. Even if it is, there is still absolutely no guarantee that the vaddr value it returns is valid for virt_to_page() - on many systems it will be in vmalloc or some architecture-specific region of address space. The problem is not that these drivers are buggy (they're not - the arch code is returning a vmalloc()ed non-cacheable remap in the first place), it's that 26abe88e830d is fundamentally unworkable and needs reverting. Apparently the original patches managed not to catch my eye as something I needed to review, sorry about that :( Robin. > > So if a buggy driver passes in a good value for 'dma' but a bad value > for 'vaddr', then it may have appeared to work previously (but with > possible data corruption, depending on the circumstances), but my patch > will expose the problem. You can confirm by reverting my dmapool > patches and enabling DMAPOOL_DEBUG, which is at the top of mm/dmapool.c: > > #if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON) > #define DMAPOOL_DEBUG 1 > #endif > > Tony Battersby > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next 2018-12-06 15:51 ` Robin Murphy @ 2018-12-06 16:13 ` Tony Battersby -1 siblings, 0 replies; 14+ messages in thread From: Tony Battersby @ 2018-12-06 16:13 UTC (permalink / raw) To: Robin Murphy, Krzysztof Kozlowski, tony, akpm Cc: Stephen Rothwell, john.garry, linux, linux-kernel, andy.shevchenko, linux-omap, hch, linux-arm-kernel, Marek Szyprowski, Matthew Wilcox On 12/6/18 10:51 AM, Robin Murphy wrote: >> Here is the prototype: >> >> void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); >> >> With the old code, the 'dma' value had to be correct for use with >> pool_find_page(), or else you would get an error. If the 'vaddr' value >> was incorrect, it would corrupt the dmapool freelist, but you wouldn't >> get an error unless DMAPOOL_DEBUG was enabled. >> >> With my patch applied, 'vaddr' has to be correct for virt_to_page(). My >> code also checks that 'dma' is consistent with 'vaddr' even if >> DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent >> problems like this in the future. > Unfortunately that logic has a fatal flaw - DMA pools are backed by > dma_alloc_coherent(), and there is absolutely no guarantee that the > memory dma_alloc_coherent() returns is backed by a struct page at all. > Even if it is, there is still absolutely no guarantee that the vaddr > value it returns is valid for virt_to_page() - on many systems it will > be in vmalloc or some architecture-specific region of address space. > > The problem is not that these drivers are buggy (they're not - the arch > code is returning a vmalloc()ed non-cacheable remap in the first place), > it's that 26abe88e830d is fundamentally unworkable and needs reverting. > Apparently the original patches managed not to catch my eye as something > I needed to review, sorry about that :( > > Robin. > Thanks for the info; the inner workings of the vm system are a bit out of my area of expertise. My first version of the patch series used a different method that didn't rely on virt_to_page(); I will go back to that version, clean it up, and resubmit when I have time. Andrew, please revert all 9 patches. I will resubmit the set when I have a workable solution. Tony Battersby ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next @ 2018-12-06 16:13 ` Tony Battersby 0 siblings, 0 replies; 14+ messages in thread From: Tony Battersby @ 2018-12-06 16:13 UTC (permalink / raw) To: Robin Murphy, Krzysztof Kozlowski, tony, akpm Cc: Stephen Rothwell, john.garry, linux, Matthew Wilcox, linux-kernel, andy.shevchenko, linux-omap, hch, linux-arm-kernel, Marek Szyprowski On 12/6/18 10:51 AM, Robin Murphy wrote: >> Here is the prototype: >> >> void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); >> >> With the old code, the 'dma' value had to be correct for use with >> pool_find_page(), or else you would get an error. If the 'vaddr' value >> was incorrect, it would corrupt the dmapool freelist, but you wouldn't >> get an error unless DMAPOOL_DEBUG was enabled. >> >> With my patch applied, 'vaddr' has to be correct for virt_to_page(). My >> code also checks that 'dma' is consistent with 'vaddr' even if >> DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent >> problems like this in the future. > Unfortunately that logic has a fatal flaw - DMA pools are backed by > dma_alloc_coherent(), and there is absolutely no guarantee that the > memory dma_alloc_coherent() returns is backed by a struct page at all. > Even if it is, there is still absolutely no guarantee that the vaddr > value it returns is valid for virt_to_page() - on many systems it will > be in vmalloc or some architecture-specific region of address space. > > The problem is not that these drivers are buggy (they're not - the arch > code is returning a vmalloc()ed non-cacheable remap in the first place), > it's that 26abe88e830d is fundamentally unworkable and needs reverting. > Apparently the original patches managed not to catch my eye as something > I needed to review, sorry about that :( > > Robin. > Thanks for the info; the inner workings of the vm system are a bit out of my area of expertise. My first version of the patch series used a different method that didn't rely on virt_to_page(); I will go back to that version, clean it up, and resubmit when I have time. Andrew, please revert all 9 patches. I will resubmit the set when I have a workable solution. Tony Battersby _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next 2018-12-06 16:13 ` Tony Battersby @ 2018-12-06 16:33 ` Tony Lindgren -1 siblings, 0 replies; 14+ messages in thread From: Tony Lindgren @ 2018-12-06 16:33 UTC (permalink / raw) To: Tony Battersby Cc: Robin Murphy, Krzysztof Kozlowski, akpm, Stephen Rothwell, john.garry, linux, linux-kernel, andy.shevchenko, linux-omap, hch, linux-arm-kernel, Marek Szyprowski, Matthew Wilcox * Tony Battersby <tonyb@cybernetics.com> [181206 16:13]: > On 12/6/18 10:51 AM, Robin Murphy wrote: > >> Here is the prototype: > >> > >> void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); > >> > >> With the old code, the 'dma' value had to be correct for use with > >> pool_find_page(), or else you would get an error. If the 'vaddr' value > >> was incorrect, it would corrupt the dmapool freelist, but you wouldn't > >> get an error unless DMAPOOL_DEBUG was enabled. > >> > >> With my patch applied, 'vaddr' has to be correct for virt_to_page(). My > >> code also checks that 'dma' is consistent with 'vaddr' even if > >> DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent > >> problems like this in the future. > > Unfortunately that logic has a fatal flaw - DMA pools are backed by > > dma_alloc_coherent(), and there is absolutely no guarantee that the > > memory dma_alloc_coherent() returns is backed by a struct page at all. > > Even if it is, there is still absolutely no guarantee that the vaddr > > value it returns is valid for virt_to_page() - on many systems it will > > be in vmalloc or some architecture-specific region of address space. > > > > The problem is not that these drivers are buggy (they're not - the arch > > code is returning a vmalloc()ed non-cacheable remap in the first place), > > it's that 26abe88e830d is fundamentally unworkable and needs reverting. > > Apparently the original patches managed not to catch my eye as something > > I needed to review, sorry about that :( > > > > Robin. > > > Thanks for the info; the inner workings of the vm system are a bit out > of my area of expertise. My first version of the patch series used a > different method that didn't rely on virt_to_page(); I will go back to > that version, clean it up, and resubmit when I have time. > > Andrew, please revert all 9 patches. I will resubmit the set when I > have a workable solution. OK sounds good to me. I can test the new set easily when available if you Cc me on them. Thanks, Tony ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next @ 2018-12-06 16:33 ` Tony Lindgren 0 siblings, 0 replies; 14+ messages in thread From: Tony Lindgren @ 2018-12-06 16:33 UTC (permalink / raw) To: Tony Battersby Cc: Stephen Rothwell, john.garry, linux, Krzysztof Kozlowski, linux-kernel, andy.shevchenko, Matthew Wilcox, akpm, linux-omap, Robin Murphy, hch, linux-arm-kernel, Marek Szyprowski * Tony Battersby <tonyb@cybernetics.com> [181206 16:13]: > On 12/6/18 10:51 AM, Robin Murphy wrote: > >> Here is the prototype: > >> > >> void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); > >> > >> With the old code, the 'dma' value had to be correct for use with > >> pool_find_page(), or else you would get an error. If the 'vaddr' value > >> was incorrect, it would corrupt the dmapool freelist, but you wouldn't > >> get an error unless DMAPOOL_DEBUG was enabled. > >> > >> With my patch applied, 'vaddr' has to be correct for virt_to_page(). My > >> code also checks that 'dma' is consistent with 'vaddr' even if > >> DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent > >> problems like this in the future. > > Unfortunately that logic has a fatal flaw - DMA pools are backed by > > dma_alloc_coherent(), and there is absolutely no guarantee that the > > memory dma_alloc_coherent() returns is backed by a struct page at all. > > Even if it is, there is still absolutely no guarantee that the vaddr > > value it returns is valid for virt_to_page() - on many systems it will > > be in vmalloc or some architecture-specific region of address space. > > > > The problem is not that these drivers are buggy (they're not - the arch > > code is returning a vmalloc()ed non-cacheable remap in the first place), > > it's that 26abe88e830d is fundamentally unworkable and needs reverting. > > Apparently the original patches managed not to catch my eye as something > > I needed to review, sorry about that :( > > > > Robin. > > > Thanks for the info; the inner workings of the vm system are a bit out > of my area of expertise. My first version of the patch series used a > different method that didn't rely on virt_to_page(); I will go back to > that version, clean it up, and resubmit when I have time. > > Andrew, please revert all 9 patches. I will resubmit the set when I > have a workable solution. OK sounds good to me. I can test the new set easily when available if you Cc me on them. Thanks, Tony _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next 2018-12-06 16:33 ` Tony Lindgren @ 2018-12-06 22:10 ` Stephen Rothwell -1 siblings, 0 replies; 14+ messages in thread From: Stephen Rothwell @ 2018-12-06 22:10 UTC (permalink / raw) To: Tony Lindgren Cc: Tony Battersby, Robin Murphy, Krzysztof Kozlowski, akpm, john.garry, linux, linux-kernel, andy.shevchenko, linux-omap, hch, linux-arm-kernel, Marek Szyprowski, Matthew Wilcox [-- Attachment #1: Type: text/plain, Size: 2363 bytes --] Hi all, On Thu, 6 Dec 2018 08:33:15 -0800 Tony Lindgren <tony@atomide.com> wrote: > > * Tony Battersby <tonyb@cybernetics.com> [181206 16:13]: > > On 12/6/18 10:51 AM, Robin Murphy wrote: > > >> Here is the prototype: > > >> > > >> void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); > > >> > > >> With the old code, the 'dma' value had to be correct for use with > > >> pool_find_page(), or else you would get an error. If the 'vaddr' value > > >> was incorrect, it would corrupt the dmapool freelist, but you wouldn't > > >> get an error unless DMAPOOL_DEBUG was enabled. > > >> > > >> With my patch applied, 'vaddr' has to be correct for virt_to_page(). My > > >> code also checks that 'dma' is consistent with 'vaddr' even if > > >> DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent > > >> problems like this in the future. > > > Unfortunately that logic has a fatal flaw - DMA pools are backed by > > > dma_alloc_coherent(), and there is absolutely no guarantee that the > > > memory dma_alloc_coherent() returns is backed by a struct page at all. > > > Even if it is, there is still absolutely no guarantee that the vaddr > > > value it returns is valid for virt_to_page() - on many systems it will > > > be in vmalloc or some architecture-specific region of address space. > > > > > > The problem is not that these drivers are buggy (they're not - the arch > > > code is returning a vmalloc()ed non-cacheable remap in the first place), > > > it's that 26abe88e830d is fundamentally unworkable and needs reverting. > > > Apparently the original patches managed not to catch my eye as something > > > I needed to review, sorry about that :( > > > > > > Robin. > > > > > Thanks for the info; the inner workings of the vm system are a bit out > > of my area of expertise. My first version of the patch series used a > > different method that didn't rely on virt_to_page(); I will go back to > > that version, clean it up, and resubmit when I have time. > > > > Andrew, please revert all 9 patches. I will resubmit the set when I > > have a workable solution. > > OK sounds good to me. I can test the new set easily when available > if you Cc me on them. I have removed those patches from linux-next for today. -- Cheers, Stephen Rothwell [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 488 bytes --] ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: dmapool regression in next @ 2018-12-06 22:10 ` Stephen Rothwell 0 siblings, 0 replies; 14+ messages in thread From: Stephen Rothwell @ 2018-12-06 22:10 UTC (permalink / raw) To: Tony Lindgren Cc: john.garry, linux, Krzysztof Kozlowski, linux-kernel, andy.shevchenko, hch, Matthew Wilcox, akpm, linux-omap, Robin Murphy, Tony Battersby, linux-arm-kernel, Marek Szyprowski [-- Attachment #1.1: Type: text/plain, Size: 2363 bytes --] Hi all, On Thu, 6 Dec 2018 08:33:15 -0800 Tony Lindgren <tony@atomide.com> wrote: > > * Tony Battersby <tonyb@cybernetics.com> [181206 16:13]: > > On 12/6/18 10:51 AM, Robin Murphy wrote: > > >> Here is the prototype: > > >> > > >> void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma); > > >> > > >> With the old code, the 'dma' value had to be correct for use with > > >> pool_find_page(), or else you would get an error. If the 'vaddr' value > > >> was incorrect, it would corrupt the dmapool freelist, but you wouldn't > > >> get an error unless DMAPOOL_DEBUG was enabled. > > >> > > >> With my patch applied, 'vaddr' has to be correct for virt_to_page(). My > > >> code also checks that 'dma' is consistent with 'vaddr' even if > > >> DMAPOOL_DEBUG is disabled, since the check is fast and it will prevent > > >> problems like this in the future. > > > Unfortunately that logic has a fatal flaw - DMA pools are backed by > > > dma_alloc_coherent(), and there is absolutely no guarantee that the > > > memory dma_alloc_coherent() returns is backed by a struct page at all. > > > Even if it is, there is still absolutely no guarantee that the vaddr > > > value it returns is valid for virt_to_page() - on many systems it will > > > be in vmalloc or some architecture-specific region of address space. > > > > > > The problem is not that these drivers are buggy (they're not - the arch > > > code is returning a vmalloc()ed non-cacheable remap in the first place), > > > it's that 26abe88e830d is fundamentally unworkable and needs reverting. > > > Apparently the original patches managed not to catch my eye as something > > > I needed to review, sorry about that :( > > > > > > Robin. > > > > > Thanks for the info; the inner workings of the vm system are a bit out > > of my area of expertise. My first version of the patch series used a > > different method that didn't rely on virt_to_page(); I will go back to > > that version, clean it up, and resubmit when I have time. > > > > Andrew, please revert all 9 patches. I will resubmit the set when I > > have a workable solution. > > OK sounds good to me. I can test the new set easily when available > if you Cc me on them. I have removed those patches from linux-next for today. -- Cheers, Stephen Rothwell [-- Attachment #1.2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 488 bytes --] [-- Attachment #2: Type: text/plain, Size: 176 bytes --] _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2018-12-06 22:26 UTC | newest] Thread overview: 14+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2018-12-06 1:30 dmapool regression in next Tony Lindgren 2018-12-06 1:30 ` Tony Lindgren 2018-12-06 9:25 ` Krzysztof Kozlowski 2018-12-06 9:25 ` Krzysztof Kozlowski 2018-12-06 15:11 ` Tony Battersby 2018-12-06 15:11 ` Tony Battersby 2018-12-06 15:51 ` Robin Murphy 2018-12-06 15:51 ` Robin Murphy 2018-12-06 16:13 ` Tony Battersby 2018-12-06 16:13 ` Tony Battersby 2018-12-06 16:33 ` Tony Lindgren 2018-12-06 16:33 ` Tony Lindgren 2018-12-06 22:10 ` Stephen Rothwell 2018-12-06 22:10 ` Stephen Rothwell
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