From c06b6d70feb32d28f04ba37aa3df17973fd37b6b Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Fri, 15 Apr 2016 18:23:00 -0700 Subject: xen/x86: don't lose event interrupts On slow platforms with unreliable TSC, such as QEMU emulated machines, it is possible for the kernel to request the next event in the past. In that case, in the current implementation of xen_vcpuop_clockevent, we simply return -ETIME. To be precise the Xen returns -ETIME and we pass it on. However the result of this is a missed event, which simply causes the kernel to hang. Instead it is better to always ask the hypervisor for a timer event, even if the timeout is in the past. That way there are no lost interrupts and the kernel survives. To do that, remove the VCPU_SSHOTTMR_future flag. Signed-off-by: Stefano Stabellini Acked-by: Juergen Gross --- arch/x86/xen/time.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index a0a4e554c6f1..6deba5bc7e34 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -290,11 +290,11 @@ static int xen_vcpuop_set_next_event(unsigned long delta, WARN_ON(!clockevent_state_oneshot(evt)); single.timeout_abs_ns = get_abs_timeout(delta); - single.flags = VCPU_SSHOTTMR_future; + /* Get an event anyway, even if the timeout is already expired */ + single.flags = 0; ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single); - - BUG_ON(ret != 0 && ret != -ETIME); + BUG_ON(ret != 0); return ret; } -- cgit v1.2.1 From dd14be92fbf5bc1ef7343f34968440e44e21b46a Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Wed, 18 May 2016 16:44:54 +0200 Subject: xen: use same main loop for counting and remapping pages Instead of having two functions for cycling through the E820 map in order to count to be remapped pages and remap them later, just use one function with a caller supplied sub-function called for each region to be processed. This eliminates the possibility of a mismatch between both loops which showed up in certain configurations. Suggested-by: Ed Swierk Signed-off-by: Juergen Gross Cc: Signed-off-by: David Vrabel --- arch/x86/xen/setup.c | 65 +++++++++++++++++++++------------------------------- 1 file changed, 26 insertions(+), 39 deletions(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index 7ab29518a3b9..e345891450c3 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -393,6 +393,9 @@ static unsigned long __init xen_set_identity_and_remap_chunk( unsigned long i = 0; unsigned long n = end_pfn - start_pfn; + if (remap_pfn == 0) + remap_pfn = nr_pages; + while (i < n) { unsigned long cur_pfn = start_pfn + i; unsigned long left = n - i; @@ -438,17 +441,29 @@ static unsigned long __init xen_set_identity_and_remap_chunk( return remap_pfn; } -static void __init xen_set_identity_and_remap(unsigned long nr_pages) +static unsigned long __init xen_count_remap_pages( + unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages, + unsigned long remap_pages) +{ + if (start_pfn >= nr_pages) + return remap_pages; + + return remap_pages + min(end_pfn, nr_pages) - start_pfn; +} + +static unsigned long __init xen_foreach_remap_area(unsigned long nr_pages, + unsigned long (*func)(unsigned long start_pfn, unsigned long end_pfn, + unsigned long nr_pages, unsigned long last_val)) { phys_addr_t start = 0; - unsigned long last_pfn = nr_pages; + unsigned long ret_val = 0; const struct e820entry *entry = xen_e820_map; int i; /* * Combine non-RAM regions and gaps until a RAM region (or the - * end of the map) is reached, then set the 1:1 map and - * remap the memory in those non-RAM regions. + * end of the map) is reached, then call the provided function + * to perform its duty on the non-RAM region. * * The combined non-RAM regions are rounded to a whole number * of pages so any partial pages are accessible via the 1:1 @@ -466,14 +481,13 @@ static void __init xen_set_identity_and_remap(unsigned long nr_pages) end_pfn = PFN_UP(entry->addr); if (start_pfn < end_pfn) - last_pfn = xen_set_identity_and_remap_chunk( - start_pfn, end_pfn, nr_pages, - last_pfn); + ret_val = func(start_pfn, end_pfn, nr_pages, + ret_val); start = end; } } - pr_info("Released %ld page(s)\n", xen_released_pages); + return ret_val; } /* @@ -596,35 +610,6 @@ static void __init xen_ignore_unusable(void) } } -static unsigned long __init xen_count_remap_pages(unsigned long max_pfn) -{ - unsigned long extra = 0; - unsigned long start_pfn, end_pfn; - const struct e820entry *entry = xen_e820_map; - int i; - - end_pfn = 0; - for (i = 0; i < xen_e820_map_entries; i++, entry++) { - start_pfn = PFN_DOWN(entry->addr); - /* Adjacent regions on non-page boundaries handling! */ - end_pfn = min(end_pfn, start_pfn); - - if (start_pfn >= max_pfn) - return extra + max_pfn - end_pfn; - - /* Add any holes in map to result. */ - extra += start_pfn - end_pfn; - - end_pfn = PFN_UP(entry->addr + entry->size); - end_pfn = min(end_pfn, max_pfn); - - if (entry->type != E820_RAM) - extra += end_pfn - start_pfn; - } - - return extra; -} - bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size) { struct e820entry *entry; @@ -804,7 +789,7 @@ char * __init xen_memory_setup(void) max_pages = xen_get_max_pages(); /* How many extra pages do we need due to remapping? */ - max_pages += xen_count_remap_pages(max_pfn); + max_pages += xen_foreach_remap_area(max_pfn, xen_count_remap_pages); if (max_pages > max_pfn) extra_pages += max_pages - max_pfn; @@ -922,7 +907,9 @@ char * __init xen_memory_setup(void) * Set identity map on non-RAM pages and prepare remapping the * underlying RAM. */ - xen_set_identity_and_remap(max_pfn); + xen_foreach_remap_area(max_pfn, xen_set_identity_and_remap_chunk); + + pr_info("Released %ld page(s)\n", xen_released_pages); return "Xen"; } -- cgit v1.2.1