Commit 2f3a57ee authored by Alex Bennée's avatar Alex Bennée
Browse files

cputlb: ensure we save the IOTLB data in case of reset 



Any write to a device might cause a re-arrangement of memory
triggering a TLB flush and potential re-size of the TLB invalidating
previous entries. This would cause users of qemu_plugin_get_hwaddr()
to see the warning:

  invalid use of qemu_plugin_get_hwaddr

because of the failed tlb_lookup which should always succeed. To
prevent this we save the IOTLB data in case it is later needed by a
plugin doing a lookup.

Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Message-Id: <20200713200415.26214-7-alex.bennee@linaro.org>
parent 777dddc5

accel/tcg/cputlb.c

+35 −3
Original line number Diff line number Diff line
@@ -1073,6 +1073,24 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry, 
    return val;

}



/*

 * Save a potentially trashed IOTLB entry for later lookup by plugin.

 *

 * We also need to track the thread storage address because the RCU

 * cleanup that runs when we leave the critical region (the current

 * execution) is actually in a different thread.

 */

static void save_iotlb_data(CPUState *cs, hwaddr addr,

                            MemoryRegionSection *section, hwaddr mr_offset)

{

#ifdef CONFIG_PLUGIN

    SavedIOTLB *saved = &cs->saved_iotlb;

    saved->addr = addr;

    saved->section = section;

    saved->mr_offset = mr_offset;

#endif

}



static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry,

                      int mmu_idx, uint64_t val, target_ulong addr,

                      uintptr_t retaddr, MemOp op)
@@ -1092,6 +1110,12 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry, 
    }

    cpu->mem_io_pc = retaddr;



    /*

     * The memory_region_dispatch may trigger a flush/resize

     * so for plugins we save the iotlb_data just in case.

     */

    save_iotlb_data(cpu, iotlbentry->addr, section, mr_offset);



    if (mr->global_locking && !qemu_mutex_iothread_locked()) {

        qemu_mutex_lock_iothread();

        locked = true;
@@ -1381,8 +1405,11 @@ void *tlb_vaddr_to_host(CPUArchState *env, abi_ptr addr, 
 * in the softmmu lookup code (or helper). We don't handle re-fills or

 * checking the victim table. This is purely informational.

 *

 * This should never fail as the memory access being instrumented

 * should have just filled the TLB.

 * This almost never fails as the memory access being instrumented

 * should have just filled the TLB. The one corner case is io_writex

 * which can cause TLB flushes and potential resizing of the TLBs

 * loosing the information we need. In those cases we need to recover

 * data from a copy of the io_tlb entry.

 */



bool tlb_plugin_lookup(CPUState *cpu, target_ulong addr, int mmu_idx,
@@ -1406,8 +1433,13 @@ bool tlb_plugin_lookup(CPUState *cpu, target_ulong addr, int mmu_idx, 
            data->v.ram.hostaddr = addr + tlbe->addend;

        }

        return true;

    } else {

        SavedIOTLB *saved = &cpu->saved_iotlb;

        data->is_io = true;

        data->v.io.section = saved->section;

        data->v.io.offset = saved->mr_offset;

        return true;

    }

    return false;

}



#endif

include/hw/core/cpu.h

+16 −0
Original line number Diff line number Diff line
@@ -259,6 +259,18 @@ struct CPUWatchpoint { 
    QTAILQ_ENTRY(CPUWatchpoint) entry;

};



#ifdef CONFIG_PLUGIN

/*

 * For plugins we sometime need to save the resolved iotlb data before

 * the memory regions get moved around  by io_writex.

 */

typedef struct SavedIOTLB {

    hwaddr addr;

    MemoryRegionSection *section;

    hwaddr mr_offset;

} SavedIOTLB;

#endif



struct KVMState;

struct kvm_run;
@@ -417,7 +429,11 @@ struct CPUState { 


    DECLARE_BITMAP(plugin_mask, QEMU_PLUGIN_EV_MAX);



#ifdef CONFIG_PLUGIN

    GArray *plugin_mem_cbs;

    /* saved iotlb data from io_writex */

    SavedIOTLB saved_iotlb;

#endif



    /* TODO Move common fields from CPUArchState here. */

    int cpu_index;

include/qemu/typedefs.h

+1 −0
Original line number Diff line number Diff line
@@ -116,6 +116,7 @@ typedef struct QObject QObject; 
typedef struct QString QString;

typedef struct RAMBlock RAMBlock;

typedef struct Range Range;

typedef struct SavedIOTLB SavedIOTLB;

typedef struct SHPCDevice SHPCDevice;

typedef struct SSIBus SSIBus;

typedef struct VirtIODevice VirtIODevice;